diff --git a/CONTRIBUTING.md b/CONTRIBUTING.md
index 92137572..cf3a552c 100644
--- a/CONTRIBUTING.md
+++ b/CONTRIBUTING.md
@@ -82,7 +82,7 @@ How? Let's split the command down into its components:
  - `install` tells pip to use the *install* action
  - `-e` installs a project in [editable mode](https://pip.pypa.io/en/stable/reference/pip_install/#editable-installs)
  - `.` installs what's in the current directory
- - `[dev]` adds some [extra requirements](https://pythonhosted.org/setuptools/setuptools.html#declaring-extras-optional-features-with-their-own-dependencies) to the installation. (If you are curious, open `setup.py` and look for `dev` in the `extras_require` section.)
+ - `[dev]` adds some [extra requirements](https://setuptools.readthedocs.io/en/latest/setuptools.html#declaring-extras-optional-features-with-their-own-dependencies) to the installation. (If you are curious, open `setup.py` and look for `dev` in the `extras_require` section.)
 
 Aside: An alternative to `pip install -e .[dev]` is `python setup.py develop`.
 
diff --git a/PYTHON_STYLE_GUIDE.md b/PYTHON_STYLE_GUIDE.md
index ca94c197..a2a9800b 100644
--- a/PYTHON_STYLE_GUIDE.md
+++ b/PYTHON_STYLE_GUIDE.md
@@ -65,6 +65,14 @@ x = 'name: {}; score: {}'.format(name, n)
 we use the `format()` version. The [official Python documentation says](https://docs.python.org/2/library/stdtypes.html#str.format), "This method of string formatting is the new standard in Python 3, and should be preferred to the % formatting described in String Formatting Operations in new code."
 
 
+## Runnng the Flake8 Style Checker
+
+We use [Flake8](http://flake8.pycqa.org/en/latest/index.html) to check our Python code style. Once you have it installed, you can run it using:
+```text
+flake8 --max-line-length 119 bigchaindb/
+```
+
+
 ## Writing and Running (Python) Unit Tests
 
 We write unit tests for our Python code using the [pytest](http://pytest.org/latest/) framework.
diff --git a/Release_Process.md b/Release_Process.md
new file mode 100644
index 00000000..bb826ae9
--- /dev/null
+++ b/Release_Process.md
@@ -0,0 +1,23 @@
+# Our Release Process
+
+This is a summary of the steps we go through to release a new version of BigchainDB Server.
+
+1. Update the `CHANGELOG.md` file
+2. Update the version numbers in `bigchaindb/version.py`. Note that we try to use [semantic versioning](http://semver.org/) (i.e. MAJOR.MINOR.PATCH)
+3. Go to the [bigchaindb/bigchaindb Releases page on GitHub](https://github.com/bigchaindb/bigchaindb/releases)
+   and click the "Draft a new release" button
+4. Name the tag something like v0.7.0
+5. The target should be a specific commit: the one when the update of `bigchaindb/version.py` got merged into master
+6. The release title should be something like v0.7.0
+7. The description should be copied from the `CHANGELOG.md` file updated above
+8. Generate and send the latest `bigchaindb` package to PyPI. Dimi and Sylvain can do this, maybe others
+9. Login to readthedocs.org as a maintainer of the BigchainDB Server docs.
+   Go to Admin --> Versions and under **Choose Active Versions**, make sure that the new version's tag is
+   "Active" and "Public"
+
+After the release:
+
+1. Update `bigchaindb/version.py` again, to be something like 0.8.0.dev (with a dev on the end).
+This is so people reading the latest docs will know that they're for the latest (master branch)
+version of BigchainDB Server, not the docs at the time of the most recent release (which are also
+available).
diff --git a/bigchaindb/commands/bigchain.py b/bigchaindb/commands/bigchain.py
index d52131ab..217aeeb1 100644
--- a/bigchaindb/commands/bigchain.py
+++ b/bigchaindb/commands/bigchain.py
@@ -1,6 +1,5 @@
 """Implementation of the `bigchaindb` command,
-which is one of the commands in the BigchainDB
-command-line interface.
+the command-line interface (CLI) for BigchainDB Server.
 """
 
 import os
@@ -194,7 +193,7 @@ def _run_load(tx_left, stats):
     b = bigchaindb.Bigchain()
 
     while True:
-        tx = Transaction.create([b.me], [b.me])
+        tx = Transaction.create([b.me], [([b.me], 1)])
         tx = tx.sign([b.me_private])
         b.write_transaction(tx)
 
diff --git a/bigchaindb/common/crypto.py b/bigchaindb/common/crypto.py
index a0b5a71d..acce02d9 100644
--- a/bigchaindb/common/crypto.py
+++ b/bigchaindb/common/crypto.py
@@ -14,5 +14,6 @@ def generate_key_pair():
     private_key, public_key = crypto.ed25519_generate_key_pair()
     return private_key.decode(), public_key.decode()
 
+
 PrivateKey = crypto.Ed25519SigningKey
 PublicKey = crypto.Ed25519VerifyingKey
diff --git a/bigchaindb/common/exceptions.py b/bigchaindb/common/exceptions.py
index 2e1dc670..72e300fd 100644
--- a/bigchaindb/common/exceptions.py
+++ b/bigchaindb/common/exceptions.py
@@ -69,9 +69,9 @@ class CyclicBlockchainError(Exception):
     """Raised when there is a cycle in the blockchain"""
 
 
-class FulfillmentNotInValidBlock(Exception):
-    """Raised when a transaction depends on an invalid or undecided
-    fulfillment"""
+class TransactionNotInValidBlock(Exception):
+    """Raised when a transfer transaction is attempting to fulfill the
+    conditions of a transaction that is in an invalid or undecided block"""
 
 
 class AssetIdMismatch(Exception):
diff --git a/bigchaindb/common/transaction.py b/bigchaindb/common/transaction.py
index c55ab83e..18a50640 100644
--- a/bigchaindb/common/transaction.py
+++ b/bigchaindb/common/transaction.py
@@ -3,13 +3,13 @@ from functools import reduce
 from uuid import uuid4
 
 from cryptoconditions import (Fulfillment as CCFulfillment,
-                              ThresholdSha256Fulfillment, Ed25519Fulfillment,
-                              PreimageSha256Fulfillment)
+                              ThresholdSha256Fulfillment, Ed25519Fulfillment)
 from cryptoconditions.exceptions import ParsingError
 
 from bigchaindb.common.crypto import PrivateKey, hash_data
 from bigchaindb.common.exceptions import (KeypairMismatchException,
-                                          InvalidHash, InvalidSignature)
+                                          InvalidHash, InvalidSignature,
+                                          AmountError, AssetIdMismatch)
 from bigchaindb.common.util import serialize, gen_timestamp
 
 
@@ -96,6 +96,14 @@ class Fulfillment(object):
             ffill['fid'] = fid
         return ffill
 
+    @classmethod
+    def generate(cls, owners_before):
+        # TODO: write docstring
+        # The amount here does not really matter. It is only use on the
+        # condition data model but here we only care about the fulfillment
+        condition = Condition.generate(owners_before, 1)
+        return cls(condition.fulfillment, condition.owners_after)
+
     @classmethod
     def from_dict(cls, ffill):
         """Transforms a Python dictionary to a Fulfillment object.
@@ -265,7 +273,7 @@ class Condition(object):
         return cond
 
     @classmethod
-    def generate(cls, owners_after):
+    def generate(cls, owners_after, amount):
         """Generates a Condition from a specifically formed tuple or list.
 
             Note:
@@ -275,34 +283,24 @@ class Condition(object):
 
                 [(address|condition)*, [(address|condition)*, ...], ...]
 
-                If however, the thresholds of individual threshold conditions
-                to be created have to be set specifically, a tuple of the
-                following structure is necessary:
-
-                ([(address|condition)*,
-                  ([(address|condition)*, ...], subthreshold),
-                  ...], threshold)
-
             Args:
-                owners_after (:obj:`list` of :obj:`str`|tuple): The users that
-                    should be able to fulfill the Condition that is being
-                    created.
+                owners_after (:obj:`list` of :obj:`str`): The public key of
+                    the users that should be able to fulfill the Condition
+                    that is being created.
+                amount (:obj:`int`): The amount locked by the condition.
 
             Returns:
                 A Condition that can be used in a Transaction.
 
-            Returns:
+            Raises:
                 TypeError: If `owners_after` is not an instance of `list`.
-                TypeError: If `owners_after` is an empty list.
+                ValueError: If `owners_after` is an empty list.
         """
-        # TODO: We probably want to remove the tuple logic for weights here
-        # again:
-        # github.com/bigchaindb/bigchaindb/issues/730#issuecomment-255144756
-        if isinstance(owners_after, tuple):
-            owners_after, threshold = owners_after
-        else:
-            threshold = len(owners_after)
-
+        threshold = len(owners_after)
+        if not isinstance(amount, int):
+            raise TypeError('`amount` must be a int')
+        if amount < 1:
+            raise AmountError('`amount` needs to be greater than zero')
         if not isinstance(owners_after, list):
             raise TypeError('`owners_after` must be an instance of list')
         if len(owners_after) == 0:
@@ -313,12 +311,12 @@ class Condition(object):
                 ffill = Ed25519Fulfillment(public_key=owners_after[0])
             except TypeError:
                 ffill = owners_after[0]
-            return cls(ffill, owners_after)
+            return cls(ffill, owners_after, amount=amount)
         else:
             initial_cond = ThresholdSha256Fulfillment(threshold=threshold)
             threshold_cond = reduce(cls._gen_condition, owners_after,
                                     initial_cond)
-            return cls(threshold_cond, owners_after)
+            return cls(threshold_cond, owners_after, amount=amount)
 
     @classmethod
     def _gen_condition(cls, initial, current):
@@ -338,14 +336,11 @@ class Condition(object):
             Returns:
                 :class:`cryptoconditions.ThresholdSha256Fulfillment`:
         """
-        if isinstance(current, tuple):
-            owners_after, threshold = current
-        else:
-            owners_after = current
-            try:
-                threshold = len(owners_after)
-            except TypeError:
-                threshold = None
+        owners_after = current
+        try:
+            threshold = len(owners_after)
+        except TypeError:
+            threshold = None
 
         if isinstance(owners_after, list) and len(owners_after) > 1:
             ffill = ThresholdSha256Fulfillment(threshold=threshold)
@@ -420,7 +415,7 @@ class Asset(object):
         self.updatable = updatable
         self.refillable = refillable
 
-        self._validate_asset()
+        self.validate_asset()
 
     def __eq__(self, other):
         try:
@@ -463,7 +458,38 @@ class Asset(object):
         """Generates a unqiue uuid for an Asset"""
         return str(uuid4())
 
-    def _validate_asset(self):
+    @staticmethod
+    def get_asset_id(transactions):
+        """Get the asset id from a list of transaction ids.
+
+        This is useful when we want to check if the multiple inputs of a
+        transaction are related to the same asset id.
+
+        Args:
+            transactions (:obj:`list` of :class:`~bigchaindb.common.
+                transaction.Transaction`): list of transaction usually inputs
+                that should have a matching asset_id
+
+        Returns:
+            str: uuid of the asset.
+
+        Raises:
+            AssetIdMismatch: If the inputs are related to different assets.
+        """
+
+        if not isinstance(transactions, list):
+            transactions = [transactions]
+
+        # create a set of asset_ids
+        asset_ids = {tx.asset.data_id for tx in transactions}
+
+        # check that all the transasctions have the same asset_id
+        if len(asset_ids) > 1:
+            raise AssetIdMismatch(('All inputs of all transactions passed'
+                                   ' need to have the same asset id'))
+        return asset_ids.pop()
+
+    def validate_asset(self, amount=None):
         """Validates the asset"""
         if self.data is not None and not isinstance(self.data, dict):
             raise TypeError('`data` must be a dict instance or None')
@@ -474,6 +500,77 @@ class Asset(object):
         if not isinstance(self.updatable, bool):
             raise TypeError('`updatable` must be a boolean')
 
+        if self.refillable:
+            raise NotImplementedError('Refillable assets are not yet'
+                                      ' implemented')
+        if self.updatable:
+            raise NotImplementedError('Updatable assets are not yet'
+                                      ' implemented')
+
+        # If the amount is supplied we can perform extra validations to
+        # the asset
+        if amount is not None:
+            if not isinstance(amount, int):
+                raise TypeError('`amount` must be an int')
+
+            if self.divisible is False and amount != 1:
+                raise AmountError('non divisible assets always have'
+                                  ' amount equal to one')
+
+            # Since refillable assets are not yet implemented this should
+            # raise and exception
+            if self.divisible is True and amount < 2:
+                raise AmountError('divisible assets must have an amount'
+                                  ' greater than one')
+
+
+class AssetLink(Asset):
+    """An object for unidirectional linking to a Asset.
+    """
+
+    def __init__(self, data_id=None):
+        """Used to point to a specific Asset.
+
+            Args:
+                data_id (str): A Asset to link to.
+        """
+        self.data_id = data_id
+
+    def __bool__(self):
+        return self.data_id is not None
+
+    def __eq__(self, other):
+        return isinstance(other, AssetLink) and \
+                self.to_dict() == other.to_dict()
+
+    @classmethod
+    def from_dict(cls, link):
+        """Transforms a Python dictionary to a AssetLink object.
+
+            Args:
+                link (dict): The link to be transformed.
+
+            Returns:
+                :class:`~bigchaindb.common.transaction.AssetLink`
+        """
+        try:
+            return cls(link['id'])
+        except TypeError:
+            return cls()
+
+    def to_dict(self):
+        """Transforms the object to a Python dictionary.
+
+            Returns:
+                (dict|None): The link as an alternative serialization format.
+        """
+        if self.data_id is None:
+            return None
+        else:
+            return {
+                'id': self.data_id
+            }
+
 
 class Metadata(object):
     """Metadata is used to store a dictionary and its hash in a Transaction."""
@@ -612,9 +709,17 @@ class Transaction(object):
         self.fulfillments = fulfillments if fulfillments else []
         self.metadata = metadata
 
+        # validate asset
+        # we know that each transaction relates to a single asset
+        # we can sum the amount of all the conditions
+        # for transactions other then CREATE we only have an id so there is
+        # nothing we can validate
+        if self.operation == self.CREATE:
+            amount = sum([condition.amount for condition in self.conditions])
+            self.asset.validate_asset(amount=amount)
+
     @classmethod
-    def create(cls, owners_before, owners_after, metadata=None, asset=None,
-               secret=None, time_expire=None):
+    def create(cls, owners_before, owners_after, metadata=None, asset=None):
         """A simple way to generate a `CREATE` transaction.
 
             Note:
@@ -622,7 +727,6 @@ class Transaction(object):
                 use cases:
                     - Ed25519
                     - ThresholdSha256
-                    - PreimageSha256.
 
                 Additionally, it provides support for the following BigchainDB
                 use cases:
@@ -637,10 +741,6 @@ class Transaction(object):
                     Transaction.
                 asset (:class:`~bigchaindb.common.transaction.Asset`): An Asset
                     to be created in this Transaction.
-                secret (binarystr, optional): A secret string to create a hash-
-                    lock Condition.
-                time_expire (int, optional): The UNIX time a Transaction is
-                    valid.
 
             Returns:
                 :class:`~bigchaindb.common.transaction.Transaction`
@@ -649,54 +749,28 @@ class Transaction(object):
             raise TypeError('`owners_before` must be a list instance')
         if not isinstance(owners_after, list):
             raise TypeError('`owners_after` must be a list instance')
+        if len(owners_before) == 0:
+            raise ValueError('`owners_before` list cannot be empty')
+        if len(owners_after) == 0:
+            raise ValueError('`owners_after` list cannot be empty')
 
         metadata = Metadata(metadata)
-        if len(owners_before) == len(owners_after) and len(owners_after) == 1:
-            # NOTE: Standard case, one owner before, one after.
-            # NOTE: For this case its sufficient to use the same
-            #       fulfillment for the fulfillment and condition.
-            ffill = Ed25519Fulfillment(public_key=owners_before[0])
-            ffill_tx = Fulfillment(ffill, owners_before)
-            cond_tx = Condition.generate(owners_after)
-            return cls(cls.CREATE, asset, [ffill_tx], [cond_tx], metadata)
+        fulfillments = []
+        conditions = []
 
-        elif len(owners_before) == len(owners_after) and len(owners_after) > 1:
-            raise NotImplementedError('Multiple inputs and outputs not'
-                                      'available for CREATE')
-            # NOTE: Multiple inputs and outputs case. Currently not supported.
-            ffills = [Fulfillment(Ed25519Fulfillment(public_key=owner_before),
-                                  [owner_before])
-                      for owner_before in owners_before]
-            conds = [Condition.generate(owners) for owners in owners_after]
-            return cls(cls.CREATE, asset, ffills, conds, metadata)
+        # generate_conditions
+        for owner_after in owners_after:
+            if not isinstance(owner_after, tuple) or len(owner_after) != 2:
+                raise ValueError(('Each `owner_after` in the list must be a'
+                                  ' tuple of `([<list of public keys>],'
+                                  ' <amount>)`'))
+            pub_keys, amount = owner_after
+            conditions.append(Condition.generate(pub_keys, amount))
 
-        elif len(owners_before) == 1 and len(owners_after) > 1:
-            # NOTE: Multiple owners case
-            cond_tx = Condition.generate(owners_after)
-            ffill = Ed25519Fulfillment(public_key=owners_before[0])
-            ffill_tx = Fulfillment(ffill, owners_before)
-            return cls(cls.CREATE, asset, [ffill_tx], [cond_tx], metadata)
+        # generate fulfillments
+        fulfillments.append(Fulfillment.generate(owners_before))
 
-        elif (len(owners_before) == 1 and len(owners_after) == 0 and
-              secret is not None):
-            # NOTE: Hashlock condition case
-            hashlock = PreimageSha256Fulfillment(preimage=secret)
-            cond_tx = Condition(hashlock.condition_uri)
-            ffill = Ed25519Fulfillment(public_key=owners_before[0])
-            ffill_tx = Fulfillment(ffill, owners_before)
-            return cls(cls.CREATE, asset, [ffill_tx], [cond_tx], metadata)
-
-        elif (len(owners_before) > 0 and len(owners_after) == 0 and
-              time_expire is not None):
-            raise NotImplementedError('Timeout conditions will be implemented '
-                                      'later')
-
-        elif (len(owners_before) > 0 and len(owners_after) == 0 and
-              secret is None):
-            raise ValueError('Define a secret to create a hashlock condition')
-
-        else:
-            raise ValueError("These are not the cases you're looking for ;)")
+        return cls(cls.CREATE, asset, fulfillments, conditions, metadata)
 
     @classmethod
     def transfer(cls, inputs, owners_after, asset, metadata=None):
@@ -743,17 +817,17 @@ class Transaction(object):
             raise ValueError('`inputs` must contain at least one item')
         if not isinstance(owners_after, list):
             raise TypeError('`owners_after` must be a list instance')
+        if len(owners_after) == 0:
+            raise ValueError('`owners_after` list cannot be empty')
 
-        # NOTE: See doc strings `Note` for description.
-        if len(inputs) == len(owners_after):
-            if len(owners_after) == 1:
-                conditions = [Condition.generate(owners_after)]
-            elif len(owners_after) > 1:
-                conditions = [Condition.generate(owners) for owners
-                              in owners_after]
-        else:
-            raise ValueError("`inputs` and `owners_after`'s count must be the "
-                             "same")
+        conditions = []
+        for owner_after in owners_after:
+            if not isinstance(owner_after, tuple) or len(owner_after) != 2:
+                raise ValueError(('Each `owner_after` in the list must be a'
+                                  ' tuple of `([<list of public keys>],'
+                                  ' <amount>)`'))
+            pub_keys, amount = owner_after
+            conditions.append(Condition.generate(pub_keys, amount))
 
         metadata = Metadata(metadata)
         inputs = deepcopy(inputs)
@@ -786,20 +860,14 @@ class Transaction(object):
                 :obj:`list` of :class:`~bigchaindb.common.transaction.
                     Fulfillment`
         """
-        inputs = []
-        if condition_indices is None or len(condition_indices) == 0:
-            # NOTE: If no condition indices are passed, we just assume to
-            #       take all conditions as inputs.
-            condition_indices = [index for index, _
-                                 in enumerate(self.conditions)]
-
-        for cid in condition_indices:
-            input_cond = self.conditions[cid]
-            ffill = Fulfillment(input_cond.fulfillment,
-                                input_cond.owners_after,
-                                TransactionLink(self.id, cid))
-            inputs.append(ffill)
-        return inputs
+        # NOTE: If no condition indices are passed, we just assume to
+        #       take all conditions as inputs.
+        return [
+            Fulfillment(self.conditions[cid].fulfillment,
+                        self.conditions[cid].owners_after,
+                        TransactionLink(self.id, cid))
+            for cid in condition_indices or range(len(self.conditions))
+        ]
 
     def add_fulfillment(self, fulfillment):
         """Adds a Fulfillment to a Transaction's list of Fulfillments.
@@ -868,13 +936,12 @@ class Transaction(object):
         key_pairs = {gen_public_key(PrivateKey(private_key)):
                      PrivateKey(private_key) for private_key in private_keys}
 
-        zippedIO = enumerate(zip(self.fulfillments, self.conditions))
-        for index, (fulfillment, condition) in zippedIO:
+        for index, fulfillment in enumerate(self.fulfillments):
             # NOTE: We clone the current transaction but only add the condition
             #       and fulfillment we're currently working on plus all
             #       previously signed ones.
             tx_partial = Transaction(self.operation, self.asset, [fulfillment],
-                                     [condition], self.metadata,
+                                     self.conditions, self.metadata,
                                      self.timestamp, self.version)
 
             tx_partial_dict = tx_partial.to_dict()
@@ -1031,14 +1098,13 @@ class Transaction(object):
         """
         input_condition_uris_count = len(input_condition_uris)
         fulfillments_count = len(self.fulfillments)
-        conditions_count = len(self.conditions)
 
         def gen_tx(fulfillment, condition, input_condition_uri=None):
             """Splits multiple IO Transactions into partial single IO
             Transactions.
             """
             tx = Transaction(self.operation, self.asset, [fulfillment],
-                             [condition], self.metadata, self.timestamp,
+                             self.conditions, self.metadata, self.timestamp,
                              self.version)
             tx_dict = tx.to_dict()
             tx_dict = Transaction._remove_signatures(tx_dict)
@@ -1049,14 +1115,13 @@ class Transaction(object):
                                                   tx_serialized,
                                                   input_condition_uri)
 
-        if not fulfillments_count == conditions_count == \
-           input_condition_uris_count:
-            raise ValueError('Fulfillments, conditions and '
+        if not fulfillments_count == input_condition_uris_count:
+            raise ValueError('Fulfillments and '
                              'input_condition_uris must have the same count')
-        else:
-            partial_transactions = map(gen_tx, self.fulfillments,
-                                       self.conditions, input_condition_uris)
-            return all(partial_transactions)
+
+        partial_transactions = map(gen_tx, self.fulfillments,
+                                   self.conditions, input_condition_uris)
+        return all(partial_transactions)
 
     @staticmethod
     def _fulfillment_valid(fulfillment, operation, tx_serialized,
@@ -1214,7 +1279,10 @@ class Transaction(object):
             conditions = [Condition.from_dict(condition) for condition
                           in tx['conditions']]
             metadata = Metadata.from_dict(tx['metadata'])
-            asset = Asset.from_dict(tx['asset'])
+            if tx['operation'] in [cls.CREATE, cls.GENESIS]:
+                asset = Asset.from_dict(tx['asset'])
+            else:
+                asset = AssetLink.from_dict(tx['asset'])
 
             return cls(tx['operation'], asset, fulfillments, conditions,
                        metadata, tx['timestamp'], tx_body['version'])
diff --git a/bigchaindb/core.py b/bigchaindb/core.py
index 4df29dd1..a7be4983 100644
--- a/bigchaindb/core.py
+++ b/bigchaindb/core.py
@@ -6,7 +6,7 @@ from time import time
 from itertools import compress
 from bigchaindb.common import crypto, exceptions
 from bigchaindb.common.util import gen_timestamp, serialize
-from bigchaindb.common.transaction import TransactionLink
+from bigchaindb.common.transaction import TransactionLink, Asset
 
 import bigchaindb
 
@@ -182,12 +182,35 @@ class Bigchain(object):
 
         try:
             return self.validate_transaction(transaction)
-        except (ValueError, exceptions.OperationError, exceptions.TransactionDoesNotExist,
+        except (ValueError, exceptions.OperationError,
+                exceptions.TransactionDoesNotExist,
                 exceptions.TransactionOwnerError, exceptions.DoubleSpend,
                 exceptions.InvalidHash, exceptions.InvalidSignature,
-                exceptions.FulfillmentNotInValidBlock):
+                exceptions.TransactionNotInValidBlock, exceptions.AmountError):
             return False
 
+    def get_block(self, block_id, include_status=False):
+        """Get the block with the specified `block_id` (and optionally its status)
+
+        Returns the block corresponding to `block_id` or None if no match is
+        found.
+
+        Args:
+            block_id (str): transaction id of the transaction to get
+            include_status (bool): also return the status of the block
+                       the return value is then a tuple: (block, status)
+        """
+        block = self.backend.get_block(block_id)
+        status = None
+
+        if include_status:
+            if block:
+                status = self.block_election_status(block_id,
+                                                    block['block']['voters'])
+            return block, status
+        else:
+            return block
+
     def get_transaction(self, txid, include_status=False):
         """Get the transaction with the specified `txid` (and optionally its status)
 
@@ -343,6 +366,21 @@ class Bigchain(object):
         cursor = self.backend.get_transactions_by_asset_id(asset_id)
         return [Transaction.from_dict(tx) for tx in cursor]
 
+    def get_asset_by_id(self, asset_id):
+        """Returns the asset associated with an asset_id.
+
+            Args:
+                asset_id (str): The asset id.
+
+            Returns:
+                :class:`~bigchaindb.common.transaction.Asset` if the asset
+                exists else None.
+        """
+        cursor = self.backend.get_asset_by_id(asset_id)
+        cursor = list(cursor)
+        if cursor:
+            return Asset.from_dict(cursor[0]['transaction']['asset'])
+
     def get_spent(self, txid, cid):
         """Check if a `txid` was already used as an input.
 
@@ -511,7 +549,7 @@ class Bigchain(object):
         """Prepare a genesis block."""
 
         metadata = {'message': 'Hello World from the BigchainDB'}
-        transaction = Transaction.create([self.me], [self.me],
+        transaction = Transaction.create([self.me], [([self.me], 1)],
                                          metadata=metadata)
 
         # NOTE: The transaction model doesn't expose an API to generate a
diff --git a/bigchaindb/db/backends/rethinkdb.py b/bigchaindb/db/backends/rethinkdb.py
index 22937dd2..b9355b41 100644
--- a/bigchaindb/db/backends/rethinkdb.py
+++ b/bigchaindb/db/backends/rethinkdb.py
@@ -178,7 +178,27 @@ class RethinkDBBackend:
             r.table('bigchain', read_mode=self.read_mode)
              .get_all(asset_id, index='asset_id')
              .concat_map(lambda block: block['block']['transactions'])
-             .filter(lambda transaction: transaction['transaction']['asset']['id'] == asset_id))
+             .filter(lambda transaction:
+                     transaction['transaction']['asset']['id'] == asset_id))
+
+    def get_asset_by_id(self, asset_id):
+        """Returns the asset associated with an asset_id.
+
+            Args:
+                asset_id (str): The asset id.
+
+            Returns:
+                Returns a rethinkdb cursor.
+        """
+        return self.connection.run(
+            r.table('bigchain', read_mode=self.read_mode)
+             .get_all(asset_id, index='asset_id')
+             .concat_map(lambda block: block['block']['transactions'])
+             .filter(lambda transaction:
+                     transaction['transaction']['asset']['id'] == asset_id)
+             .filter(lambda transaction:
+                     transaction['transaction']['operation'] == 'CREATE')
+             .pluck({'transaction': 'asset'}))
 
     def get_spent(self, transaction_id, condition_id):
         """Check if a `txid` was already used as an input.
@@ -258,6 +278,17 @@ class RethinkDBBackend:
                 r.table('bigchain')
                 .insert(r.json(block), durability=durability))
 
+    def get_block(self, block_id):
+        """Get a block from the bigchain table
+
+        Args:
+            block_id (str): block id of the block to get
+
+        Returns:
+            block (dict): the block or `None`
+        """
+        return self.connection.run(r.table('bigchain').get(block_id))
+
     def has_transaction(self, transaction_id):
         """Check if a transaction exists in the bigchain table.
 
@@ -282,6 +313,17 @@ class RethinkDBBackend:
                 r.table('bigchain', read_mode=self.read_mode)
                 .count())
 
+    def count_backlog(self):
+        """Count the number of transactions in the backlog table.
+
+        Returns:
+            The number of transactions in the backlog.
+        """
+
+        return self.connection.run(
+                r.table('backlog', read_mode=self.read_mode)
+                .count())
+
     def write_vote(self, vote):
         """Write a vote to the votes table.
 
@@ -295,6 +337,17 @@ class RethinkDBBackend:
                 r.table('votes')
                 .insert(vote))
 
+    def get_genesis_block(self):
+        """Get the genesis block
+
+        Returns:
+            The genesis block
+        """
+        return self.connection.run(
+            r.table('bigchain', read_mode=self.read_mode)
+            .filter(util.is_genesis_block)
+            .nth(0))
+
     def get_last_voted_block(self, node_pubkey):
         """Get the last voted block for a specific node.
 
@@ -319,10 +372,7 @@ class RethinkDBBackend:
 
         except r.ReqlNonExistenceError:
             # return last vote if last vote exists else return Genesis block
-            return self.connection.run(
-                r.table('bigchain', read_mode=self.read_mode)
-                .filter(util.is_genesis_block)
-                .nth(0))
+            return self.get_genesis_block()
 
         # Now the fun starts. Since the resolution of timestamp is a second,
         # we might have more than one vote per timestamp. If this is the case
diff --git a/bigchaindb/models.py b/bigchaindb/models.py
index 5aa697cb..3bbc80e3 100644
--- a/bigchaindb/models.py
+++ b/bigchaindb/models.py
@@ -2,42 +2,12 @@ from bigchaindb.common.crypto import hash_data, PublicKey, PrivateKey
 from bigchaindb.common.exceptions import (InvalidHash, InvalidSignature,
                                           OperationError, DoubleSpend,
                                           TransactionDoesNotExist,
-                                          FulfillmentNotInValidBlock,
-                                          AssetIdMismatch)
+                                          TransactionNotInValidBlock,
+                                          AssetIdMismatch, AmountError)
 from bigchaindb.common.transaction import Transaction, Asset
 from bigchaindb.common.util import gen_timestamp, serialize
 
 
-class Asset(Asset):
-    @staticmethod
-    def get_asset_id(transactions):
-        """Get the asset id from a list of transaction ids.
-
-        This is useful when we want to check if the multiple inputs of a transaction
-        are related to the same asset id.
-
-        Args:
-            transactions (list): list of transaction usually inputs that should have a matching asset_id
-
-        Returns:
-            str: uuid of the asset.
-
-        Raises:
-            AssetIdMismatch: If the inputs are related to different assets.
-        """
-
-        if not isinstance(transactions, list):
-            transactions = [transactions]
-
-        # create a set of asset_ids
-        asset_ids = {tx.asset.data_id for tx in transactions}
-
-        # check that all the transasctions have the same asset_id
-        if len(asset_ids) > 1:
-            raise AssetIdMismatch("All inputs of a transaction need to have the same asset id.")
-        return asset_ids.pop()
-
-
 class Transaction(Transaction):
     def validate(self, bigchain):
         """Validate a transaction.
@@ -54,6 +24,8 @@ class Transaction(Transaction):
             OperationError: if the transaction operation is not supported
             TransactionDoesNotExist: if the input of the transaction is not
                                      found
+            TransactionNotInValidBlock: if the input of the transaction is not
+                                        in a valid block
             TransactionOwnerError: if the new transaction is using an input it
                                    doesn't own
             DoubleSpend: if the transaction is a double spend
@@ -71,7 +43,8 @@ class Transaction(Transaction):
             if inputs_defined:
                 raise ValueError('A CREATE operation has no inputs')
             # validate asset
-            self.asset._validate_asset()
+            amount = sum([condition.amount for condition in self.conditions])
+            self.asset.validate_asset(amount=amount)
         elif self.operation == Transaction.TRANSFER:
             if not inputs_defined:
                 raise ValueError('Only `CREATE` transactions can have null '
@@ -79,6 +52,7 @@ class Transaction(Transaction):
             # check inputs
             # store the inputs so that we can check if the asset ids match
             input_txs = []
+            input_amount = 0
             for ffill in self.fulfillments:
                 input_txid = ffill.tx_input.txid
                 input_cid = ffill.tx_input.cid
@@ -90,7 +64,7 @@ class Transaction(Transaction):
                                                   .format(input_txid))
 
                 if status != bigchain.TX_VALID:
-                    raise FulfillmentNotInValidBlock(
+                    raise TransactionNotInValidBlock(
                         'input `{}` does not exist in a valid block'.format(
                             input_txid))
 
@@ -101,11 +75,34 @@ class Transaction(Transaction):
 
                 input_conditions.append(input_tx.conditions[input_cid])
                 input_txs.append(input_tx)
+                if input_tx.conditions[input_cid].amount < 1:
+                    raise AmountError('`amount` needs to be greater than zero')
+                input_amount += input_tx.conditions[input_cid].amount
 
             # validate asset id
             asset_id = Asset.get_asset_id(input_txs)
             if asset_id != self.asset.data_id:
-                raise AssetIdMismatch('The asset id of the input does not match the asset id of the transaction')
+                raise AssetIdMismatch(('The asset id of the input does not'
+                                       ' match the asset id of the'
+                                       ' transaction'))
+
+            # get the asset creation to see if its divisible or not
+            asset = bigchain.get_asset_by_id(asset_id)
+            # validate the asset
+            asset.validate_asset(amount=input_amount)
+            # validate the amounts
+            output_amount = 0
+            for condition in self.conditions:
+                if condition.amount < 1:
+                    raise AmountError('`amount` needs to be greater than zero')
+                output_amount += condition.amount
+
+            if output_amount != input_amount:
+                raise AmountError(('The amount used in the inputs `{}`'
+                                   ' needs to be same as the amount used'
+                                   ' in the outputs `{}`')
+                                  .format(input_amount, output_amount))
+
         else:
             allowed_operations = ', '.join(Transaction.ALLOWED_OPERATIONS)
             raise TypeError('`operation`: `{}` must be either {}.'
@@ -118,8 +115,36 @@ class Transaction(Transaction):
 
 
 class Block(object):
+    """Bundle a list of Transactions in a Block. Nodes vote on its validity.
+
+    Attributes:
+        transaction (:obj:`list` of :class:`~.Transaction`):
+            Transactions to be included in the Block.
+        node_pubkey (str): The public key of the node creating the
+            Block.
+        timestamp (str): The Unix time a Block was created.
+        voters (:obj:`list` of :obj:`str`): A list of a federation
+            nodes' public keys supposed to vote on the Block.
+        signature (str): A cryptographic signature ensuring the
+            integrity and validity of the creator of a Block.
+    """
+
     def __init__(self, transactions=None, node_pubkey=None, timestamp=None,
                  voters=None, signature=None):
+        """The Block model is mainly used for (de)serialization and integrity
+        checking.
+
+        Args:
+            transaction (:obj:`list` of :class:`~.Transaction`):
+                Transactions to be included in the Block.
+            node_pubkey (str): The public key of the node creating the
+                Block.
+            timestamp (str): The Unix time a Block was created.
+            voters (:obj:`list` of :obj:`str`): A list of a federation
+                nodes' public keys supposed to vote on the Block.
+            signature (str): A cryptographic signature ensuring the
+                integrity and validity of the creator of a Block.
+        """
         if transactions is not None and not isinstance(transactions, list):
             raise TypeError('`transactions` must be a list instance or None')
         else:
@@ -146,18 +171,20 @@ class Block(object):
         return self.to_dict() == other
 
     def validate(self, bigchain):
-        """Validate a block.
+        """Validate the Block.
 
         Args:
-            bigchain (Bigchain): an instantiated bigchaindb.Bigchain object.
+            bigchain (:class:`~bigchaindb.Bigchain`): An instantiated Bigchain
+                object.
 
         Returns:
-            block (Block): The block as a `Block` object if it is valid.
-                           Else it raises an appropriate exception describing
-                           the reason of invalidity.
+            :class:`~.Block`: If valid, return a `Block` object. Else an
+            appropriate exception describing the reason of invalidity is
+            raised.
 
         Raises:
-            OperationError: if a non-federation node signed the block.
+            OperationError: If a non-federation node signed the Block.
+            InvalidSignature: If a Block's signature is invalid.
         """
 
         # First, make sure this node hasn't already voted on this block
@@ -182,6 +209,15 @@ class Block(object):
         return self
 
     def sign(self, private_key):
+        """Create a signature for the Block and overwrite `self.signature`.
+
+        Args:
+            private_key (str): A private key corresponding to
+                `self.node_pubkey`.
+
+        Returns:
+            :class:`~.Block`
+        """
         block_body = self.to_dict()
         block_serialized = serialize(block_body['block'])
         private_key = PrivateKey(private_key)
@@ -189,8 +225,13 @@ class Block(object):
         return self
 
     def is_signature_valid(self):
+        """Check the validity of a Block's signature.
+
+        Returns:
+            bool: Stating the validity of the Block's signature.
+        """
         block = self.to_dict()['block']
-        # cc only accepts bytesting messages
+        # cc only accepts bytestring messages
         block_serialized = serialize(block).encode()
         public_key = PublicKey(block['node_pubkey'])
         try:
@@ -202,6 +243,21 @@ class Block(object):
 
     @classmethod
     def from_dict(cls, block_body):
+        """Transform a Python dictionary to a Block object.
+
+        Args:
+            block_body (dict): A block dictionary to be transformed.
+
+        Returns:
+            :class:`~Block`
+
+        Raises:
+            InvalidHash: If the block's id is not corresponding to its
+                data.
+            InvalidSignature: If the block's signature is not corresponding
+                to it's data or `node_pubkey`.
+        """
+        # TODO: Reuse `is_signature_valid` method here.
         block = block_body['block']
         block_serialized = serialize(block)
         block_id = hash_data(block_serialized)
@@ -237,6 +293,14 @@ class Block(object):
         return self.to_dict()['id']
 
     def to_dict(self):
+        """Transform the Block to a Python dictionary.
+
+        Returns:
+            dict: The Block as a dict.
+
+        Raises:
+            OperationError: If the Block doesn't contain any transactions.
+        """
         if len(self.transactions) == 0:
             raise OperationError('Empty block creation is not allowed')
 
diff --git a/bigchaindb/pipelines/vote.py b/bigchaindb/pipelines/vote.py
index 6b12f55b..b89e0786 100644
--- a/bigchaindb/pipelines/vote.py
+++ b/bigchaindb/pipelines/vote.py
@@ -40,10 +40,11 @@ class Vote:
         self.validity = {}
 
         self.invalid_dummy_tx = Transaction.create([self.bigchain.me],
-                                                   [self.bigchain.me])
+                                                   [([self.bigchain.me], 1)])
 
     def validate_block(self, block):
-        if not self.bigchain.has_previous_vote(block['id'], block['block']['voters']):
+        if not self.bigchain.has_previous_vote(block['id'],
+                                               block['block']['voters']):
             try:
                 block = Block.from_dict(block)
             except (exceptions.InvalidHash, exceptions.InvalidSignature):
diff --git a/bigchaindb/web/server.py b/bigchaindb/web/server.py
index 50ef4cc3..1756fffe 100644
--- a/bigchaindb/web/server.py
+++ b/bigchaindb/web/server.py
@@ -49,19 +49,22 @@ class StandaloneApplication(gunicorn.app.base.BaseApplication):
         return self.application
 
 
-def create_app(settings):
+def create_app(*, debug=False, threads=4):
     """Return an instance of the Flask application.
 
     Args:
         debug (bool): a flag to activate the debug mode for the app
             (default: False).
+        threads (int): number of threads to use
+    Return:
+        an instance of the Flask application.
     """
 
     app = Flask(__name__)
 
-    app.debug = settings.get('debug', False)
+    app.debug = debug
 
-    app.config['bigchain_pool'] = util.pool(Bigchain, size=settings.get('threads', 4))
+    app.config['bigchain_pool'] = util.pool(Bigchain, size=threads)
     app.config['monitor'] = Monitor()
 
     app.register_blueprint(info_views, url_prefix='/')
@@ -88,6 +91,7 @@ def create_server(settings):
     if not settings.get('threads'):
         settings['threads'] = (multiprocessing.cpu_count() * 2) + 1
 
-    app = create_app(settings)
+    app = create_app(debug=settings.get('debug', False),
+                     threads=settings['threads'])
     standalone = StandaloneApplication(app, settings)
     return standalone
diff --git a/bigchaindb/web/views/transactions.py b/bigchaindb/web/views/transactions.py
index 8780fda8..c529b6b3 100644
--- a/bigchaindb/web/views/transactions.py
+++ b/bigchaindb/web/views/transactions.py
@@ -111,6 +111,7 @@ class TransactionListApi(Resource):
 
         return tx
 
+
 transaction_api.add_resource(TransactionApi,
                              '/transactions/<string:tx_id>',
                              strict_slashes=False)
diff --git a/docs/root/source/index.rst b/docs/root/source/index.rst
index 39235cad..c8ddb1ff 100644
--- a/docs/root/source/index.rst
+++ b/docs/root/source/index.rst
@@ -58,6 +58,9 @@ At a high level, one can communicate with a BigchainDB cluster (set of nodes) us
    <div class="buttondiv">
      <a class="button" href="http://docs.bigchaindb.com/projects/py-driver/en/latest/index.html">Python Driver Docs</a>
    </div>
+   <div class="buttondiv">
+     <a class="button" href="https://docs.bigchaindb.com/projects/cli/en/latest/">Command Line Transaction Tool</a>
+   </div>
    <div class="buttondiv">
      <a class="button" href="http://docs.bigchaindb.com/projects/server/en/latest/index.html">Server Docs</a>
    </div>
diff --git a/docs/server/source/drivers-clients/http-client-server-api.rst b/docs/server/source/drivers-clients/http-client-server-api.rst
index 74bcf1d2..f50b4f98 100644
--- a/docs/server/source/drivers-clients/http-client-server-api.rst
+++ b/docs/server/source/drivers-clients/http-client-server-api.rst
@@ -3,21 +3,35 @@ The HTTP Client-Server API
 
 .. note::
 
-   The HTTP client-server API is currently quite rudimentary. For example, there is no ability to do complex queries using the HTTP API. We plan to add querying capabilities in the future.
+   The HTTP client-server API is currently quite rudimentary. For example,
+   there is no ability to do complex queries using the HTTP API. We plan to add
+   querying capabilities in the future.
 
-When you start Bigchaindb using `bigchaindb start`, an HTTP API is exposed at the address stored in the BigchainDB node configuration settings. The default is:
+When you start Bigchaindb using `bigchaindb start`, an HTTP API is exposed at
+the address stored in the BigchainDB node configuration settings. The default
+is:
 
 `http://localhost:9984/api/v1/ <http://localhost:9984/api/v1/>`_
 
-but that address can be changed by changing the "API endpoint" configuration setting (e.g. in a local config file). There's more information about setting the API endpoint in :doc:`the section about BigchainDB Configuration Settings <../server-reference/configuration>`.
+but that address can be changed by changing the "API endpoint" configuration
+setting (e.g. in a local config file). There's more information about setting
+the API endpoint in :doc:`the section about BigchainDB Configuration Settings
+<../server-reference/configuration>`.
 
-There are other configuration settings related to the web server (serving the HTTP API). In particular, the default is for the web server socket to bind to ``localhost:9984`` but that can be changed (e.g. to ``0.0.0.0:9984``). For more details, see the "server" settings ("bind", "workers" and "threads") in :doc:`the section about BigchainDB Configuration Settings <../server-reference/configuration>`.
+There are other configuration settings related to the web server (serving the
+HTTP API). In particular, the default is for the web server socket to bind to
+``localhost:9984`` but that can be changed (e.g. to ``0.0.0.0:9984``). For more
+details, see the "server" settings ("bind", "workers" and "threads") in
+:doc:`the section about BigchainDB Configuration Settings
+<../server-reference/configuration>`.
 
 
 API Root
 --------
 
-If you send an HTTP GET request to e.g. ``http://localhost:9984`` (with no ``/api/v1/`` on the end), then you should get an HTTP response with something like the following in the body:
+If you send an HTTP GET request to e.g. ``http://localhost:9984`` (with no
+``/api/v1/`` on the end), then you should get an HTTP response with something
+like the following in the body:
 
 .. code-block:: json
 
@@ -39,8 +53,13 @@ POST /transactions/
 .. http:post:: /transactions/
 
    Push a new transaction.
-   
-   Note: The posted transaction should be valid `transaction <https://bigchaindb.readthedocs.io/en/latest/data-models/transaction-model.html>`_. The steps to build a valid transaction are beyond the scope of this page. One would normally use a driver such as the `BigchainDB Python Driver <https://docs.bigchaindb.com/projects/py-driver/en/latest/index.html>`_ to build a valid transaction.
+
+   Note: The posted transaction should be valid `transaction
+   <https://bigchaindb.readthedocs.io/en/latest/data-models/transaction-model.html>`_.
+   The steps to build a valid transaction are beyond the scope of this page.
+   One would normally use a driver such as the `BigchainDB Python Driver
+   <https://docs.bigchaindb.com/projects/py-driver/en/latest/index.html>`_ to
+   build a valid transaction.
 
    **Example request**:
 
@@ -158,9 +177,11 @@ GET /transactions/{tx_id}/status
 
 .. http:get:: /transactions/{tx_id}/status
 
-   Get the status of the transaction with the ID ``tx_id``, if a transaction with that ``tx_id`` exists.
+   Get the status of the transaction with the ID ``tx_id``, if a transaction
+   with that ``tx_id`` exists.
 
-   The possible status values are ``backlog``, ``undecided``, ``valid`` or ``invalid``.
+   The possible status values are ``backlog``, ``undecided``, ``valid`` or
+   ``invalid``.
 
    :param tx_id: transaction ID
    :type tx_id: hex string
@@ -194,7 +215,8 @@ GET /transactions/{tx_id}
 
    Get the transaction with the ID ``tx_id``.
 
-   This endpoint returns only a transaction from a ``VALID`` or ``UNDECIDED`` block on ``bigchain``, if exists.
+   This endpoint returns only a transaction from a ``VALID`` or ``UNDECIDED``
+   block on ``bigchain``, if exists.
 
    :param tx_id: transaction ID
    :type tx_id: hex string
@@ -260,4 +282,46 @@ GET /transactions/{tx_id}
       }
 
    :statuscode 200: A transaction with that ID was found.
-   :statuscode 404: A transaction with that ID was not found.
\ No newline at end of file
+   :statuscode 404: A transaction with that ID was not found.
+
+
+GET /unspents/
+-------------------------
+
+.. http:get:: /unspents?owner_after={owner_after}
+
+   Get a list of links to transactions' conditions that have not been used in
+   a previous transaction and could hence be called unspent conditions/outputs
+   (or simply: unspents).
+
+   This endpoint will return a ``HTTP 400 Bad Request`` if the querystring
+   ``owner_after`` happens to not be defined in the request.
+
+   Note that if unspents for a certain ``owner_after`` have not been found by
+   the server, this will result in the server returning a 200 OK HTTP status
+   code and an empty list in the response's body.
+
+   :param owner_after: A public key, able to validly spend an output of a transaction, assuming the user also has the corresponding private key.
+   :type owner_after: base58 encoded string
+
+   **Example request**:
+
+   .. sourcecode:: http
+
+      GET /unspents?owner_after=1AAAbbb...ccc HTTP/1.1
+      Host: example.com
+
+   **Example response**:
+
+   .. sourcecode:: http
+
+      HTTP/1.1 200 OK
+      Content-Type: application/json
+
+      [
+        '../transactions/2d431073e1477f3073a4693ac7ff9be5634751de1b8abaa1f4e19548ef0b4b0e/conditions/0',
+        '../transactions/2d431073e1477f3073a4693ac7ff9be5634751de1b8abaa1f4e19548ef0b4b0e/conditions/1'
+      ]
+
+   :statuscode 200: A list of outputs were found and returned in the body of the response.
+   :statuscode 400: The request wasn't understood by the server, e.g. the ``owner_after`` querystring was not included in the request.
diff --git a/docs/server/source/drivers-clients/index.rst b/docs/server/source/drivers-clients/index.rst
index 1c55d133..9eb81f6c 100644
--- a/docs/server/source/drivers-clients/index.rst
+++ b/docs/server/source/drivers-clients/index.rst
@@ -1,10 +1,17 @@
 Drivers & Clients
 =================
 
+Currently, the only language-native driver is written in the Python language.
+
+We also provide the Transaction CLI to be able to script the building of
+transactions. You may be able to wrap this tool inside the language of
+your choice, and then use the HTTP API directly to post transactions.
+
+
 .. toctree::
    :maxdepth: 1
 
    http-client-server-api
-   python-driver
+   The Python Driver <https://docs.bigchaindb.com/projects/py-driver/en/latest/index.html>
+   Transaction CLI <https://docs.bigchaindb.com/projects/cli/en/latest/>
    example-apps
-   
\ No newline at end of file
diff --git a/docs/server/source/drivers-clients/python-driver.md b/docs/server/source/drivers-clients/python-driver.md
deleted file mode 100644
index 99563924..00000000
--- a/docs/server/source/drivers-clients/python-driver.md
+++ /dev/null
@@ -1,7 +0,0 @@
-# The Python Driver
-
-The BigchainDB Python Driver is a Python wrapper around the [HTTP Client-Server API](http-client-server-api.html). A developer can use it to develop a Python app that communicates with one or more BigchainDB clusters.
-
-The BigchainDB Python Driver documentation is at:
-
-[http://docs.bigchaindb.com/projects/py-driver/en/latest/index.html](http://docs.bigchaindb.com/projects/py-driver/en/latest/index.html)
diff --git a/tests/assets/test_digital_assets.py b/tests/assets/test_digital_assets.py
index 2d0c0a0a..1b0a258b 100644
--- a/tests/assets/test_digital_assets.py
+++ b/tests/assets/test_digital_assets.py
@@ -1,5 +1,7 @@
 import pytest
-from ..db.conftest import inputs
+from unittest.mock import patch
+
+from ..db.conftest import inputs  # noqa
 
 
 @pytest.mark.usefixtures('inputs')
@@ -9,7 +11,7 @@ def test_asset_transfer(b, user_pk, user_sk):
     tx_input = b.get_owned_ids(user_pk).pop()
     tx_create = b.get_transaction(tx_input.txid)
 
-    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [user_pk],
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [([user_pk], 1)],
                                        tx_create.asset)
     tx_transfer_signed = tx_transfer.sign([user_sk])
 
@@ -18,61 +20,40 @@ def test_asset_transfer(b, user_pk, user_sk):
 
 
 def test_validate_bad_asset_creation(b, user_pk):
-    from bigchaindb.models import Transaction
+    from bigchaindb.models import Transaction, Asset
 
     # `divisible` needs to be a boolean
-    tx = Transaction.create([b.me], [user_pk])
+    tx = Transaction.create([b.me], [([user_pk], 1)])
     tx.asset.divisible = 1
-    tx_signed = tx.sign([b.me_private])
+    with patch.object(Asset, 'validate_asset', return_value=None):
+        tx_signed = tx.sign([b.me_private])
     with pytest.raises(TypeError):
         tx_signed.validate(b)
 
     # `refillable` needs to be a boolean
-    tx = Transaction.create([b.me], [user_pk])
+    tx = Transaction.create([b.me], [([user_pk], 1)])
     tx.asset.refillable = 1
-    tx_signed = tx.sign([b.me_private])
+    with patch.object(Asset, 'validate_asset', return_value=None):
+        tx_signed = tx.sign([b.me_private])
     with pytest.raises(TypeError):
         b.validate_transaction(tx_signed)
 
     # `updatable` needs to be a boolean
-    tx = Transaction.create([b.me], [user_pk])
+    tx = Transaction.create([b.me], [([user_pk], 1)])
     tx.asset.updatable = 1
-    tx_signed = tx.sign([b.me_private])
+    with patch.object(Asset, 'validate_asset', return_value=None):
+        tx_signed = tx.sign([b.me_private])
     with pytest.raises(TypeError):
         b.validate_transaction(tx_signed)
 
     # `data` needs to be a dictionary
-    tx = Transaction.create([b.me], [user_pk])
+    tx = Transaction.create([b.me], [([user_pk], 1)])
     tx.asset.data = 'a'
-    tx_signed = tx.sign([b.me_private])
+    with patch.object(Asset, 'validate_asset', return_value=None):
+        tx_signed = tx.sign([b.me_private])
     with pytest.raises(TypeError):
         b.validate_transaction(tx_signed)
 
-    # TODO: Check where to test for the amount
-    """
-    tx = b.create_transaction(b.me, user_pk, None, 'CREATE')
-    tx['transaction']['conditions'][0]['amount'] = 'a'
-    tx['id'] = get_hash_data(tx['transaction'])
-    tx_signed = b.sign_transaction(tx, b.me_private)
-    with pytest.raises(TypeError):
-        b.validate_transaction(tx_signed)
-
-    tx = b.create_transaction(b.me, user_pk, None, 'CREATE')
-    tx['transaction']['conditions'][0]['amount'] = 2
-    tx['transaction']['asset'].update({'divisible': False})
-    tx['id'] = get_hash_data(tx['transaction'])
-    tx_signed = b.sign_transaction(tx, b.me_private)
-    with pytest.raises(AmountError):
-        b.validate_transaction(tx_signed)
-
-    tx = b.create_transaction(b.me, user_pk, None, 'CREATE')
-    tx['transaction']['conditions'][0]['amount'] = 0
-    tx['id'] = get_hash_data(tx['transaction'])
-    tx_signed = b.sign_transaction(tx, b.me_private)
-    with pytest.raises(AmountError):
-        b.validate_transaction(tx_signed)
-    """
-
 
 @pytest.mark.usefixtures('inputs')
 def test_validate_transfer_asset_id_mismatch(b, user_pk, user_sk):
@@ -81,7 +62,7 @@ def test_validate_transfer_asset_id_mismatch(b, user_pk, user_sk):
 
     tx_create = b.get_owned_ids(user_pk).pop()
     tx_create = b.get_transaction(tx_create.txid)
-    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [user_pk],
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [([user_pk], 1)],
                                        tx_create.asset)
     tx_transfer.asset.data_id = 'aaa'
     tx_transfer_signed = tx_transfer.sign([user_sk])
@@ -92,7 +73,7 @@ def test_validate_transfer_asset_id_mismatch(b, user_pk, user_sk):
 def test_get_asset_id_create_transaction(b, user_pk):
     from bigchaindb.models import Transaction, Asset
 
-    tx_create = Transaction.create([b.me], [user_pk])
+    tx_create = Transaction.create([b.me], [([user_pk], 1)])
     asset_id = Asset.get_asset_id(tx_create)
 
     assert asset_id == tx_create.asset.data_id
@@ -105,7 +86,7 @@ def test_get_asset_id_transfer_transaction(b, user_pk, user_sk):
     tx_create = b.get_owned_ids(user_pk).pop()
     tx_create = b.get_transaction(tx_create.txid)
     # create a transfer transaction
-    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [user_pk],
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [([user_pk], 1)],
                                        tx_create.asset)
     tx_transfer_signed = tx_transfer.sign([user_sk])
     # create a block
@@ -123,8 +104,8 @@ def test_asset_id_mismatch(b, user_pk):
     from bigchaindb.models import Transaction, Asset
     from bigchaindb.common.exceptions import AssetIdMismatch
 
-    tx1 = Transaction.create([b.me], [user_pk])
-    tx2 = Transaction.create([b.me], [user_pk])
+    tx1 = Transaction.create([b.me], [([user_pk], 1)])
+    tx2 = Transaction.create([b.me], [([user_pk], 1)])
 
     with pytest.raises(AssetIdMismatch):
         Asset.get_asset_id([tx1, tx2])
@@ -144,7 +125,7 @@ def test_get_txs_by_asset_id(b, user_pk, user_sk):
     assert txs[0].asset.data_id == asset_id
 
     # create a transfer transaction
-    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [user_pk],
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [([user_pk], 1)],
                                        tx_create.asset)
     tx_transfer_signed = tx_transfer.sign([user_sk])
     # create the block
@@ -161,3 +142,73 @@ def test_get_txs_by_asset_id(b, user_pk, user_sk):
     assert tx_transfer.id in [t.id for t in txs]
     assert asset_id == txs[0].asset.data_id
     assert asset_id == txs[1].asset.data_id
+
+
+@pytest.mark.usefixtures('inputs')
+def test_get_asset_by_id(b, user_vk, user_sk):
+    from bigchaindb.models import Transaction
+
+    tx_create = b.get_owned_ids(user_vk).pop()
+    tx_create = b.get_transaction(tx_create.txid)
+    asset_id = tx_create.asset.data_id
+
+    # create a transfer transaction
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [([user_vk], 1)],
+                                       tx_create.asset)
+    tx_transfer_signed = tx_transfer.sign([user_sk])
+    # create the block
+    block = b.create_block([tx_transfer_signed])
+    b.write_block(block, durability='hard')
+    # vote the block valid
+    vote = b.vote(block.id, b.get_last_voted_block().id, True)
+    b.write_vote(vote)
+
+    txs = b.get_txs_by_asset_id(asset_id)
+    assert len(txs) == 2
+
+    asset = b.get_asset_by_id(asset_id)
+    assert asset == tx_create.asset
+
+
+def test_create_invalid_divisible_asset(b, user_vk, user_sk):
+    from bigchaindb.models import Transaction, Asset
+    from bigchaindb.common.exceptions import AmountError
+
+    # non divisible assets cannot have amount > 1
+    # Transaction.__init__ should raise an exception
+    asset = Asset(divisible=False)
+    with pytest.raises(AmountError):
+        Transaction.create([user_vk], [([user_vk], 2)], asset=asset)
+
+    # divisible assets need to have an amount > 1
+    # Transaction.__init__ should raise an exception
+    asset = Asset(divisible=True)
+    with pytest.raises(AmountError):
+        Transaction.create([user_vk], [([user_vk], 1)], asset=asset)
+
+    # even if a transaction is badly constructed the server should raise the
+    # exception
+    asset = Asset(divisible=False)
+    with patch.object(Asset, 'validate_asset', return_value=None):
+        tx = Transaction.create([user_vk], [([user_vk], 2)], asset=asset)
+        tx_signed = tx.sign([user_sk])
+    with pytest.raises(AmountError):
+        tx_signed.validate(b)
+    assert b.is_valid_transaction(tx_signed) is False
+
+    asset = Asset(divisible=True)
+    with patch.object(Asset, 'validate_asset', return_value=None):
+        tx = Transaction.create([user_vk], [([user_vk], 1)], asset=asset)
+        tx_signed = tx.sign([user_sk])
+    with pytest.raises(AmountError):
+        tx_signed.validate(b)
+    assert b.is_valid_transaction(tx_signed) is False
+
+
+def test_create_valid_divisible_asset(b, user_vk, user_sk):
+    from bigchaindb.models import Transaction, Asset
+
+    asset = Asset(divisible=True)
+    tx = Transaction.create([user_vk], [([user_vk], 2)], asset=asset)
+    tx_signed = tx.sign([user_sk])
+    assert b.is_valid_transaction(tx_signed)
diff --git a/tests/assets/test_divisible_assets.py b/tests/assets/test_divisible_assets.py
new file mode 100644
index 00000000..5ae360e0
--- /dev/null
+++ b/tests/assets/test_divisible_assets.py
@@ -0,0 +1,779 @@
+import pytest
+
+from unittest.mock import patch
+
+from ..db.conftest import inputs  # noqa
+
+
+# CREATE divisible asset
+# Single input
+# Single owners_before
+# Single output
+# Single owners_after
+def test_single_in_single_own_single_out_single_own_create(b, user_vk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+
+    asset = Asset(divisible=True)
+    tx = Transaction.create([b.me], [([user_vk], 100)], asset=asset)
+    tx_signed = tx.sign([b.me_private])
+
+    assert tx_signed.validate(b) == tx_signed
+    assert len(tx_signed.conditions) == 1
+    assert tx_signed.conditions[0].amount == 100
+    assert len(tx_signed.fulfillments) == 1
+
+
+# CREATE divisible asset
+# Single input
+# Single owners_before
+# Multiple outputs
+# Single owners_after per output
+def test_single_in_single_own_multiple_out_single_own_create(b, user_vk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+
+    asset = Asset(divisible=True)
+    tx = Transaction.create([b.me], [([user_vk], 50), ([user_vk], 50)],
+                            asset=asset)
+    tx_signed = tx.sign([b.me_private])
+
+    assert tx_signed.validate(b) == tx_signed
+    assert len(tx_signed.conditions) == 2
+    assert tx_signed.conditions[0].amount == 50
+    assert tx_signed.conditions[1].amount == 50
+    assert len(tx_signed.fulfillments) == 1
+
+
+# CREATE divisible asset
+# Single input
+# Single owners_before
+# Single output
+# Multiple owners_after
+def test_single_in_single_own_single_out_multiple_own_create(b, user_vk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+
+    asset = Asset(divisible=True)
+    tx = Transaction.create([b.me], [([user_vk, user_vk], 100)], asset=asset)
+    tx_signed = tx.sign([b.me_private])
+
+    assert tx_signed.validate(b) == tx_signed
+    assert len(tx_signed.conditions) == 1
+    assert tx_signed.conditions[0].amount == 100
+
+    condition = tx_signed.conditions[0].to_dict()
+    assert 'subfulfillments' in condition['condition']['details']
+    assert len(condition['condition']['details']['subfulfillments']) == 2
+
+    assert len(tx_signed.fulfillments) == 1
+
+
+# CREATE divisible asset
+# Single input
+# Single owners_before
+# Multiple outputs
+# Mix: one output with a single owners_after, one output with multiple
+#      owners_after
+def test_single_in_single_own_multiple_out_mix_own_create(b, user_vk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+
+    asset = Asset(divisible=True)
+    tx = Transaction.create([b.me],
+                            [([user_vk], 50), ([user_vk, user_vk], 50)],
+                            asset=asset)
+    tx_signed = tx.sign([b.me_private])
+
+    assert tx_signed.validate(b) == tx_signed
+    assert len(tx_signed.conditions) == 2
+    assert tx_signed.conditions[0].amount == 50
+    assert tx_signed.conditions[1].amount == 50
+
+    condition_cid1 = tx_signed.conditions[1].to_dict()
+    assert 'subfulfillments' in condition_cid1['condition']['details']
+    assert len(condition_cid1['condition']['details']['subfulfillments']) == 2
+
+    assert len(tx_signed.fulfillments) == 1
+
+
+# CREATE divisible asset
+# Single input
+# Multiple owners_before
+# Output combinations already tested above
+def test_single_in_multiple_own_single_out_single_own_create(b, user_vk,
+                                                             user_sk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+
+    asset = Asset(divisible=True)
+    tx = Transaction.create([b.me, user_vk], [([user_vk], 100)], asset=asset)
+    tx_signed = tx.sign([b.me_private, user_sk])
+    assert tx_signed.validate(b) == tx_signed
+    assert len(tx_signed.conditions) == 1
+    assert tx_signed.conditions[0].amount == 100
+    assert len(tx_signed.fulfillments) == 1
+
+    ffill = tx_signed.fulfillments[0].fulfillment.to_dict()
+    assert 'subfulfillments' in ffill
+    assert len(ffill['subfulfillments']) == 2
+
+
+# TRANSFER divisible asset
+# Single input
+# Single owners_before
+# Single output
+# Single owners_after
+# TODO: I don't really need inputs. But I need the database to be setup or
+#       else there will be no genesis block and b.get_last_voted_block will
+#       fail.
+#       Is there a better way of doing this?
+@pytest.mark.usefixtures('inputs')
+def test_single_in_single_own_single_out_single_own_transfer(b, user_vk,
+                                                             user_sk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+
+    # CREATE divisible asset
+    asset = Asset(divisible=True)
+    tx_create = Transaction.create([b.me], [([user_vk], 100)], asset=asset)
+    tx_create_signed = tx_create.sign([b.me_private])
+    # create block
+    block = b.create_block([tx_create_signed])
+    assert block.validate(b) == block
+    b.write_block(block, durability='hard')
+    # vote
+    vote = b.vote(block.id, b.get_last_voted_block().id, True)
+    b.write_vote(vote)
+
+    # TRANSFER
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [([b.me], 100)],
+                                       asset=tx_create.asset)
+    tx_transfer_signed = tx_transfer.sign([user_sk])
+
+    assert tx_transfer_signed.validate(b)
+    assert len(tx_transfer_signed.conditions) == 1
+    assert tx_transfer_signed.conditions[0].amount == 100
+    assert len(tx_transfer_signed.fulfillments) == 1
+
+
+# TRANSFER divisible asset
+# Single input
+# Single owners_before
+# Multiple output
+# Single owners_after
+@pytest.mark.usefixtures('inputs')
+def test_single_in_single_own_multiple_out_single_own_transfer(b, user_vk,
+                                                               user_sk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+
+    # CREATE divisible asset
+    asset = Asset(divisible=True)
+    tx_create = Transaction.create([b.me], [([user_vk], 100)], asset=asset)
+    tx_create_signed = tx_create.sign([b.me_private])
+    # create block
+    block = b.create_block([tx_create_signed])
+    assert block.validate(b) == block
+    b.write_block(block, durability='hard')
+    # vote
+    vote = b.vote(block.id, b.get_last_voted_block().id, True)
+    b.write_vote(vote)
+
+    # TRANSFER
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(),
+                                       [([b.me], 50), ([b.me], 50)],
+                                       asset=tx_create.asset)
+    tx_transfer_signed = tx_transfer.sign([user_sk])
+
+    assert tx_transfer_signed.validate(b) == tx_transfer_signed
+    assert len(tx_transfer_signed.conditions) == 2
+    assert tx_transfer_signed.conditions[0].amount == 50
+    assert tx_transfer_signed.conditions[1].amount == 50
+    assert len(tx_transfer_signed.fulfillments) == 1
+
+
+# TRANSFER divisible asset
+# Single input
+# Single owners_before
+# Single output
+# Multiple owners_after
+@pytest.mark.usefixtures('inputs')
+def test_single_in_single_own_single_out_multiple_own_transfer(b, user_vk,
+                                                               user_sk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+
+    # CREATE divisible asset
+    asset = Asset(divisible=True)
+    tx_create = Transaction.create([b.me], [([user_vk], 100)], asset=asset)
+    tx_create_signed = tx_create.sign([b.me_private])
+    # create block
+    block = b.create_block([tx_create_signed])
+    assert block.validate(b) == block
+    b.write_block(block, durability='hard')
+    # vote
+    vote = b.vote(block.id, b.get_last_voted_block().id, True)
+    b.write_vote(vote)
+
+    # TRANSFER
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(),
+                                       [([b.me, b.me], 100)],
+                                       asset=tx_create.asset)
+    tx_transfer_signed = tx_transfer.sign([user_sk])
+
+    assert tx_transfer_signed.validate(b) == tx_transfer_signed
+    assert len(tx_transfer_signed.conditions) == 1
+    assert tx_transfer_signed.conditions[0].amount == 100
+
+    condition = tx_transfer_signed.conditions[0].to_dict()
+    assert 'subfulfillments' in condition['condition']['details']
+    assert len(condition['condition']['details']['subfulfillments']) == 2
+
+    assert len(tx_transfer_signed.fulfillments) == 1
+
+
+# TRANSFER divisible asset
+# Single input
+# Single owners_before
+# Multiple outputs
+# Mix: one output with a single owners_after, one output with multiple
+#      owners_after
+@pytest.mark.usefixtures('inputs')
+def test_single_in_single_own_multiple_out_mix_own_transfer(b, user_vk,
+                                                            user_sk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+
+    # CREATE divisible asset
+    asset = Asset(divisible=True)
+    tx_create = Transaction.create([b.me], [([user_vk], 100)], asset=asset)
+    tx_create_signed = tx_create.sign([b.me_private])
+    # create block
+    block = b.create_block([tx_create_signed])
+    assert block.validate(b) == block
+    b.write_block(block, durability='hard')
+    # vote
+    vote = b.vote(block.id, b.get_last_voted_block().id, True)
+    b.write_vote(vote)
+
+    # TRANSFER
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(),
+                                       [([b.me], 50), ([b.me, b.me], 50)],
+                                       asset=tx_create.asset)
+    tx_transfer_signed = tx_transfer.sign([user_sk])
+
+    assert tx_transfer_signed.validate(b) == tx_transfer_signed
+    assert len(tx_transfer_signed.conditions) == 2
+    assert tx_transfer_signed.conditions[0].amount == 50
+    assert tx_transfer_signed.conditions[1].amount == 50
+
+    condition_cid1 = tx_transfer_signed.conditions[1].to_dict()
+    assert 'subfulfillments' in condition_cid1['condition']['details']
+    assert len(condition_cid1['condition']['details']['subfulfillments']) == 2
+
+    assert len(tx_transfer_signed.fulfillments) == 1
+
+
+# TRANSFER divisible asset
+# Single input
+# Multiple owners_before
+# Single output
+# Single owners_after
+@pytest.mark.usefixtures('inputs')
+def test_single_in_multiple_own_single_out_single_own_transfer(b, user_vk,
+                                                               user_sk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+
+    # CREATE divisible asset
+    asset = Asset(divisible=True)
+    tx_create = Transaction.create([b.me], [([b.me, user_vk], 100)],
+                                   asset=asset)
+    tx_create_signed = tx_create.sign([b.me_private])
+    # create block
+    block = b.create_block([tx_create_signed])
+    assert block.validate(b) == block
+    b.write_block(block, durability='hard')
+    # vote
+    vote = b.vote(block.id, b.get_last_voted_block().id, True)
+    b.write_vote(vote)
+
+    # TRANSFER
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [([b.me], 100)],
+                                       asset=tx_create.asset)
+    tx_transfer_signed = tx_transfer.sign([b.me_private, user_sk])
+
+    assert tx_transfer_signed.validate(b) == tx_transfer_signed
+    assert len(tx_transfer_signed.conditions) == 1
+    assert tx_transfer_signed.conditions[0].amount == 100
+    assert len(tx_transfer_signed.fulfillments) == 1
+
+    ffill = tx_transfer_signed.fulfillments[0].fulfillment.to_dict()
+    assert 'subfulfillments' in ffill
+    assert len(ffill['subfulfillments']) == 2
+
+
+# TRANSFER divisible asset
+# Multiple inputs
+# Single owners_before per input
+# Single output
+# Single owners_after
+@pytest.mark.usefixtures('inputs')
+def test_multiple_in_single_own_single_out_single_own_transfer(b, user_vk,
+                                                               user_sk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+
+    # CREATE divisible asset
+    asset = Asset(divisible=True)
+    tx_create = Transaction.create([b.me], [([user_vk], 50), ([user_vk], 50)],
+                                   asset=asset)
+    tx_create_signed = tx_create.sign([b.me_private])
+    # create block
+    block = b.create_block([tx_create_signed])
+    assert block.validate(b) == block
+    b.write_block(block, durability='hard')
+    # vote
+    vote = b.vote(block.id, b.get_last_voted_block().id, True)
+    b.write_vote(vote)
+
+    # TRANSFER
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [([b.me], 100)],
+                                       asset=tx_create.asset)
+    tx_transfer_signed = tx_transfer.sign([user_sk])
+
+    assert tx_transfer_signed.validate(b)
+    assert len(tx_transfer_signed.conditions) == 1
+    assert tx_transfer_signed.conditions[0].amount == 100
+    assert len(tx_transfer_signed.fulfillments) == 2
+
+
+# TRANSFER divisible asset
+# Multiple inputs
+# Multiple owners_before per input
+# Single output
+# Single owners_after
+@pytest.mark.usefixtures('inputs')
+def test_multiple_in_multiple_own_single_out_single_own_transfer(b, user_vk,
+                                                                 user_sk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+
+    # CREATE divisible asset
+    asset = Asset(divisible=True)
+    tx_create = Transaction.create([b.me],
+                                   [([user_vk, b.me], 50),
+                                    ([user_vk, b.me], 50)],
+                                   asset=asset)
+    tx_create_signed = tx_create.sign([b.me_private])
+    # create block
+    block = b.create_block([tx_create_signed])
+    assert block.validate(b) == block
+    b.write_block(block, durability='hard')
+    # vote
+    vote = b.vote(block.id, b.get_last_voted_block().id, True)
+    b.write_vote(vote)
+
+    # TRANSFER
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [([b.me], 100)],
+                                       asset=tx_create.asset)
+    tx_transfer_signed = tx_transfer.sign([b.me_private, user_sk])
+
+    assert tx_transfer_signed.validate(b)
+    assert len(tx_transfer_signed.conditions) == 1
+    assert tx_transfer_signed.conditions[0].amount == 100
+    assert len(tx_transfer_signed.fulfillments) == 2
+
+    ffill_fid0 = tx_transfer_signed.fulfillments[0].fulfillment.to_dict()
+    ffill_fid1 = tx_transfer_signed.fulfillments[1].fulfillment.to_dict()
+    assert 'subfulfillments' in ffill_fid0
+    assert 'subfulfillments' in ffill_fid1
+    assert len(ffill_fid0['subfulfillments']) == 2
+    assert len(ffill_fid1['subfulfillments']) == 2
+
+
+# TRANSFER divisible asset
+# Multiple inputs
+# Mix: one input with a single owners_before, one input with multiple
+#      owners_before
+# Single output
+# Single owners_after
+@pytest.mark.usefixtures('inputs')
+def test_muiltiple_in_mix_own_multiple_out_single_own_transfer(b, user_vk,
+                                                               user_sk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+
+    # CREATE divisible asset
+    asset = Asset(divisible=True)
+    tx_create = Transaction.create([b.me],
+                                   [([user_vk], 50),
+                                    ([user_vk, b.me], 50)],
+                                   asset=asset)
+    tx_create_signed = tx_create.sign([b.me_private])
+    # create block
+    block = b.create_block([tx_create_signed])
+    assert block.validate(b) == block
+    b.write_block(block, durability='hard')
+    # vote
+    vote = b.vote(block.id, b.get_last_voted_block().id, True)
+    b.write_vote(vote)
+
+    # TRANSFER
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [([b.me], 100)],
+                                       asset=tx_create.asset)
+    tx_transfer_signed = tx_transfer.sign([b.me_private, user_sk])
+
+    assert tx_transfer_signed.validate(b) == tx_transfer_signed
+    assert len(tx_transfer_signed.conditions) == 1
+    assert tx_transfer_signed.conditions[0].amount == 100
+    assert len(tx_transfer_signed.fulfillments) == 2
+
+    ffill_fid0 = tx_transfer_signed.fulfillments[0].fulfillment.to_dict()
+    ffill_fid1 = tx_transfer_signed.fulfillments[1].fulfillment.to_dict()
+    assert 'subfulfillments' not in ffill_fid0
+    assert 'subfulfillments' in ffill_fid1
+    assert len(ffill_fid1['subfulfillments']) == 2
+
+
+# TRANSFER divisible asset
+# Multiple inputs
+# Mix: one input with a single owners_before, one input with multiple
+#      owners_before
+# Multiple outputs
+# Mix: one output with a single owners_after, one output with multiple
+#      owners_after
+@pytest.mark.usefixtures('inputs')
+def test_muiltiple_in_mix_own_multiple_out_mix_own_transfer(b, user_vk,
+                                                            user_sk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+
+    # CREATE divisible asset
+    asset = Asset(divisible=True)
+    tx_create = Transaction.create([b.me],
+                                   [([user_vk], 50),
+                                    ([user_vk, b.me], 50)],
+                                   asset=asset)
+    tx_create_signed = tx_create.sign([b.me_private])
+    # create block
+    block = b.create_block([tx_create_signed])
+    assert block.validate(b) == block
+    b.write_block(block, durability='hard')
+    # vote
+    vote = b.vote(block.id, b.get_last_voted_block().id, True)
+    b.write_vote(vote)
+
+    # TRANSFER
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(),
+                                       [([b.me], 50), ([b.me, user_vk], 50)],
+                                       asset=tx_create.asset)
+    tx_transfer_signed = tx_transfer.sign([b.me_private, user_sk])
+
+    assert tx_transfer_signed.validate(b) == tx_transfer_signed
+    assert len(tx_transfer_signed.conditions) == 2
+    assert tx_transfer_signed.conditions[0].amount == 50
+    assert tx_transfer_signed.conditions[1].amount == 50
+    assert len(tx_transfer_signed.fulfillments) == 2
+
+    cond_cid0 = tx_transfer_signed.conditions[0].to_dict()
+    cond_cid1 = tx_transfer_signed.conditions[1].to_dict()
+    assert 'subfulfillments' not in cond_cid0['condition']['details']
+    assert 'subfulfillments' in cond_cid1['condition']['details']
+    assert len(cond_cid1['condition']['details']['subfulfillments']) == 2
+
+    ffill_fid0 = tx_transfer_signed.fulfillments[0].fulfillment.to_dict()
+    ffill_fid1 = tx_transfer_signed.fulfillments[1].fulfillment.to_dict()
+    assert 'subfulfillments' not in ffill_fid0
+    assert 'subfulfillments' in ffill_fid1
+    assert len(ffill_fid1['subfulfillments']) == 2
+
+
+# TRANSFER divisible asset
+# Multiple inputs from different transactions
+# Single owners_before
+# Single output
+# Single owners_after
+@pytest.mark.usefixtures('inputs')
+def test_multiple_in_different_transactions(b, user_vk, user_sk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+
+    # CREATE divisible asset
+    # `b` creates a divisible asset and assigns 50 shares to `b` and
+    # 50 shares to `user_vk`
+    asset = Asset(divisible=True)
+    tx_create = Transaction.create([b.me],
+                                   [([user_vk], 50),
+                                    ([b.me], 50)],
+                                   asset=asset)
+    tx_create_signed = tx_create.sign([b.me_private])
+    # create block
+    block = b.create_block([tx_create_signed])
+    assert block.validate(b) == block
+    b.write_block(block, durability='hard')
+    # vote
+    vote = b.vote(block.id, b.get_last_voted_block().id, True)
+    b.write_vote(vote)
+
+    # TRANSFER divisible asset
+    # `b` transfers its 50 shares to `user_vk`
+    # after this transaction `user_vk` will have a total of 100 shares
+    # split across two different transactions
+    tx_transfer1 = Transaction.transfer(tx_create.to_inputs([1]),
+                                        [([user_vk], 50)],
+                                        asset=tx_create.asset)
+    tx_transfer1_signed = tx_transfer1.sign([b.me_private])
+    # create block
+    block = b.create_block([tx_transfer1_signed])
+    assert block.validate(b) == block
+    b.write_block(block, durability='hard')
+    # vote
+    vote = b.vote(block.id, b.get_last_voted_block().id, True)
+    b.write_vote(vote)
+
+    # TRANSFER
+    # `user_vk` combines two different transaction with 50 shares each and
+    # transfers a total of 100 shares back to `b`
+    tx_transfer2 = Transaction.transfer(tx_create.to_inputs([0]) +
+                                        tx_transfer1.to_inputs([0]),
+                                        [([b.me], 100)],
+                                        asset=tx_create.asset)
+    tx_transfer2_signed = tx_transfer2.sign([user_sk])
+
+    assert tx_transfer2_signed.validate(b) == tx_transfer2_signed
+    assert len(tx_transfer2_signed.conditions) == 1
+    assert tx_transfer2_signed.conditions[0].amount == 100
+    assert len(tx_transfer2_signed.fulfillments) == 2
+
+    fid0_input = tx_transfer2_signed.fulfillments[0].to_dict()['input']['txid']
+    fid1_input = tx_transfer2_signed.fulfillments[1].to_dict()['input']['txid']
+    assert fid0_input == tx_create.id
+    assert fid1_input == tx_transfer1.id
+
+
+# In a TRANSFER transaction of a divisible asset the amount being spent in the
+# inputs needs to match the amount being sent in the outputs.
+# In other words `amount_in_inputs - amount_in_outputs == 0`
+@pytest.mark.usefixtures('inputs')
+def test_amount_error_transfer(b, user_vk, user_sk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+    from bigchaindb.common.exceptions import AmountError
+
+    # CREATE divisible asset
+    asset = Asset(divisible=True)
+    tx_create = Transaction.create([b.me], [([user_vk], 100)], asset=asset)
+    tx_create_signed = tx_create.sign([b.me_private])
+    # create block
+    block = b.create_block([tx_create_signed])
+    assert block.validate(b) == block
+    b.write_block(block, durability='hard')
+    # vote
+    vote = b.vote(block.id, b.get_last_voted_block().id, True)
+    b.write_vote(vote)
+
+    # TRANSFER
+    # output amount less than input amount
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [([b.me], 50)],
+                                       asset=tx_create.asset)
+    tx_transfer_signed = tx_transfer.sign([user_sk])
+    with pytest.raises(AmountError):
+        tx_transfer_signed.validate(b)
+
+    # TRANSFER
+    # output amount greater than input amount
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [([b.me], 101)],
+                                       asset=tx_create.asset)
+    tx_transfer_signed = tx_transfer.sign([user_sk])
+    with pytest.raises(AmountError):
+        tx_transfer_signed.validate(b)
+
+
+@pytest.mark.skip(reason='Figure out how to handle this case')
+@pytest.mark.usefixtures('inputs')
+def test_threshold_same_public_key(b, user_vk, user_sk):
+    # If we try to fulfill a threshold condition where each subcondition has
+    # the same key get_subcondition_from_vk will always return the first
+    # subcondition. This means that only the 1st subfulfillment will be
+    # generated
+    # Creating threshold conditions with the same key does not make sense but
+    # that does not mean that the code shouldn't work.
+
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+
+    # CREATE divisible asset
+    asset = Asset(divisible=True)
+    tx_create = Transaction.create([b.me], [([user_vk, user_vk], 100)],
+                                   asset=asset)
+    tx_create_signed = tx_create.sign([b.me_private])
+    # create block
+    block = b.create_block([tx_create_signed])
+    assert block.validate(b) == block
+    b.write_block(block, durability='hard')
+    # vote
+    vote = b.vote(block.id, b.get_last_voted_block().id, True)
+    b.write_vote(vote)
+
+    # TRANSFER
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [([b.me], 100)],
+                                       asset=tx_create.asset)
+    tx_transfer_signed = tx_transfer.sign([user_sk, user_sk])
+
+    assert tx_transfer_signed.validate(b) == tx_transfer_signed
+
+
+@pytest.mark.usefixtures('inputs')
+def test_sum_amount(b, user_vk, user_sk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+
+    # CREATE divisible asset with 3 outputs with amount 1
+    asset = Asset(divisible=True)
+    tx_create = Transaction.create([b.me],
+                                   [([user_vk], 1),
+                                    ([user_vk], 1),
+                                    ([user_vk], 1)],
+                                   asset=asset)
+    tx_create_signed = tx_create.sign([b.me_private])
+    # create block
+    block = b.create_block([tx_create_signed])
+    assert block.validate(b) == block
+    b.write_block(block, durability='hard')
+    # vote
+    vote = b.vote(block.id, b.get_last_voted_block().id, True)
+    b.write_vote(vote)
+
+    # create a transfer transaction with one output and check if the amount
+    # is 3
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(), [([b.me], 3)],
+                                       asset=tx_create.asset)
+    tx_transfer_signed = tx_transfer.sign([user_sk])
+
+    assert tx_transfer_signed.validate(b) == tx_transfer_signed
+    assert len(tx_transfer_signed.conditions) == 1
+    assert tx_transfer_signed.conditions[0].amount == 3
+
+
+@pytest.mark.usefixtures('inputs')
+def test_divide(b, user_vk, user_sk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+
+    # CREATE divisible asset with 1 output with amount 3
+    asset = Asset(divisible=True)
+    tx_create = Transaction.create([b.me], [([user_vk], 3)],
+                                   asset=asset)
+    tx_create_signed = tx_create.sign([b.me_private])
+    # create block
+    block = b.create_block([tx_create_signed])
+    assert block.validate(b) == block
+    b.write_block(block, durability='hard')
+    # vote
+    vote = b.vote(block.id, b.get_last_voted_block().id, True)
+    b.write_vote(vote)
+
+    # create a transfer transaction with 3 outputs and check if the amount
+    # of each output is 1
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(),
+                                       [([b.me], 1), ([b.me], 1), ([b.me], 1)],
+                                       asset=tx_create.asset)
+    tx_transfer_signed = tx_transfer.sign([user_sk])
+
+    assert tx_transfer_signed.validate(b) == tx_transfer_signed
+    assert len(tx_transfer_signed.conditions) == 3
+    for condition in tx_transfer_signed.conditions:
+        assert condition.amount == 1
+
+
+# Check that negative inputs are caught when creating a TRANSFER transaction
+@pytest.mark.usefixtures('inputs')
+def test_non_positive_amounts_on_transfer(b, user_vk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+    from bigchaindb.common.exceptions import AmountError
+
+    # CREATE divisible asset with 1 output with amount 3
+    asset = Asset(divisible=True)
+    tx_create = Transaction.create([b.me], [([user_vk], 3)],
+                                   asset=asset)
+    tx_create_signed = tx_create.sign([b.me_private])
+    # create block
+    block = b.create_block([tx_create_signed])
+    assert block.validate(b) == block
+    b.write_block(block, durability='hard')
+    # vote
+    vote = b.vote(block.id, b.get_last_voted_block().id, True)
+    b.write_vote(vote)
+
+    with pytest.raises(AmountError):
+        Transaction.transfer(tx_create.to_inputs(),
+                             [([b.me], 4), ([b.me], -1)],
+                             asset=tx_create.asset)
+
+
+# Check that negative inputs are caught when validating a TRANSFER transaction
+@pytest.mark.usefixtures('inputs')
+def test_non_positive_amounts_on_transfer_validate(b, user_vk, user_sk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+    from bigchaindb.common.exceptions import AmountError
+
+    # CREATE divisible asset with 1 output with amount 3
+    asset = Asset(divisible=True)
+    tx_create = Transaction.create([b.me], [([user_vk], 3)],
+                                   asset=asset)
+    tx_create_signed = tx_create.sign([b.me_private])
+    # create block
+    block = b.create_block([tx_create_signed])
+    assert block.validate(b) == block
+    b.write_block(block, durability='hard')
+    # vote
+    vote = b.vote(block.id, b.get_last_voted_block().id, True)
+    b.write_vote(vote)
+
+    # create a transfer transaction with 3 outputs and check if the amount
+    # of each output is 1
+    tx_transfer = Transaction.transfer(tx_create.to_inputs(),
+                                       [([b.me], 4), ([b.me], 1)],
+                                       asset=tx_create.asset)
+    tx_transfer.conditions[1].amount = -1
+    tx_transfer_signed = tx_transfer.sign([user_sk])
+
+    with pytest.raises(AmountError):
+        tx_transfer_signed.validate(b)
+
+
+# Check that negative inputs are caught when creating a CREATE transaction
+@pytest.mark.usefixtures('inputs')
+def test_non_positive_amounts_on_create(b, user_vk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+    from bigchaindb.common.exceptions import AmountError
+
+    # CREATE divisible asset with 1 output with amount 3
+    asset = Asset(divisible=True)
+    with pytest.raises(AmountError):
+        Transaction.create([b.me], [([user_vk], -3)],
+                           asset=asset)
+
+
+# Check that negative inputs are caught when validating a CREATE transaction
+@pytest.mark.usefixtures('inputs')
+def test_non_positive_amounts_on_create_validate(b, user_vk):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.transaction import Asset
+    from bigchaindb.common.exceptions import AmountError
+
+    # CREATE divisible asset with 1 output with amount 3
+    asset = Asset(divisible=True)
+    tx_create = Transaction.create([b.me], [([user_vk], 3)],
+                                   asset=asset)
+    tx_create.conditions[0].amount = -3
+    with patch.object(Asset, 'validate_asset', return_value=None):
+        tx_create_signed = tx_create.sign([b.me_private])
+
+    with pytest.raises(AmountError):
+        tx_create_signed.validate(b)
diff --git a/tests/common/test_asset.py b/tests/common/test_asset.py
index edfbcb5f..f6a3f89d 100644
--- a/tests/common/test_asset.py
+++ b/tests/common/test_asset.py
@@ -22,6 +22,7 @@ def test_asset_creation_with_data(data):
 def test_asset_invalid_asset_initialization():
     from bigchaindb.common.transaction import Asset
 
+    # check types
     with raises(TypeError):
         Asset(data='some wrong type')
     with raises(TypeError):
@@ -31,6 +32,12 @@ def test_asset_invalid_asset_initialization():
     with raises(TypeError):
         Asset(updatable=1)
 
+    # check for features that are not yet implemented
+    with raises(NotImplementedError):
+        Asset(updatable=True)
+    with raises(NotImplementedError):
+        Asset(refillable=True)
+
 
 def test_invalid_asset_comparison(data, data_id):
     from bigchaindb.common.transaction import Asset
@@ -69,12 +76,17 @@ def test_asset_deserialization(data, data_id):
 
 def test_validate_asset():
     from bigchaindb.common.transaction import Asset
+    from bigchaindb.common.exceptions import AmountError
 
+    # test amount errors
+    asset = Asset(divisible=False)
+    with raises(AmountError):
+        asset.validate_asset(amount=2)
+
+    asset = Asset(divisible=True)
+    with raises(AmountError):
+        asset.validate_asset(amount=1)
+
+    asset = Asset()
     with raises(TypeError):
-        Asset(divisible=1)
-    with raises(TypeError):
-        Asset(refillable=1)
-    with raises(TypeError):
-        Asset(updatable=1)
-    with raises(TypeError):
-        Asset(data='we need more lemon pledge')
+        asset.validate_asset(amount='a')
diff --git a/tests/common/test_transaction.py b/tests/common/test_transaction.py
index 1a59d08b..2839ee3c 100644
--- a/tests/common/test_transaction.py
+++ b/tests/common/test_transaction.py
@@ -1,4 +1,5 @@
-from pytest import raises, mark
+from pytest import raises
+from unittest.mock import patch
 
 
 def test_fulfillment_serialization(ffill_uri, user_pub):
@@ -166,29 +167,7 @@ def test_generate_conditions_split_half_recursive(user_pub, user2_pub,
     expected_threshold.add_subfulfillment(expected_simple3)
     expected.add_subfulfillment(expected_threshold)
 
-    cond = Condition.generate([user_pub, [user2_pub, expected_simple3]])
-    assert cond.fulfillment.to_dict() == expected.to_dict()
-
-
-def test_generate_conditions_split_half_recursive_custom_threshold(user_pub,
-                                                                   user2_pub,
-                                                                   user3_pub):
-    from bigchaindb.common.transaction import Condition
-    from cryptoconditions import Ed25519Fulfillment, ThresholdSha256Fulfillment
-
-    expected_simple1 = Ed25519Fulfillment(public_key=user_pub)
-    expected_simple2 = Ed25519Fulfillment(public_key=user2_pub)
-    expected_simple3 = Ed25519Fulfillment(public_key=user3_pub)
-
-    expected = ThresholdSha256Fulfillment(threshold=1)
-    expected.add_subfulfillment(expected_simple1)
-    expected_threshold = ThresholdSha256Fulfillment(threshold=1)
-    expected_threshold.add_subfulfillment(expected_simple2)
-    expected_threshold.add_subfulfillment(expected_simple3)
-    expected.add_subfulfillment(expected_threshold)
-
-    cond = Condition.generate(([user_pub, ([user2_pub, expected_simple3], 1)],
-                              1))
+    cond = Condition.generate([user_pub, [user2_pub, expected_simple3]], 1)
     assert cond.fulfillment.to_dict() == expected.to_dict()
 
 
@@ -208,7 +187,7 @@ def test_generate_conditions_split_half_single_owner(user_pub, user2_pub,
     expected.add_subfulfillment(expected_threshold)
     expected.add_subfulfillment(expected_simple1)
 
-    cond = Condition.generate([[expected_simple2, user3_pub], user_pub])
+    cond = Condition.generate([[expected_simple2, user3_pub], user_pub], 1)
     assert cond.fulfillment.to_dict() == expected.to_dict()
 
 
@@ -225,7 +204,7 @@ def test_generate_conditions_flat_ownage(user_pub, user2_pub, user3_pub):
     expected.add_subfulfillment(expected_simple2)
     expected.add_subfulfillment(expected_simple3)
 
-    cond = Condition.generate([user_pub, user2_pub, expected_simple3])
+    cond = Condition.generate([user_pub, user2_pub, expected_simple3], 1)
     assert cond.fulfillment.to_dict() == expected.to_dict()
 
 
@@ -234,7 +213,7 @@ def test_generate_conditions_single_owner(user_pub):
     from cryptoconditions import Ed25519Fulfillment
 
     expected = Ed25519Fulfillment(public_key=user_pub)
-    cond = Condition.generate([user_pub])
+    cond = Condition.generate([user_pub], 1)
 
     assert cond.fulfillment.to_dict() == expected.to_dict()
 
@@ -244,48 +223,23 @@ def test_generate_conditions_single_owner_with_condition(user_pub):
     from cryptoconditions import Ed25519Fulfillment
 
     expected = Ed25519Fulfillment(public_key=user_pub)
-    cond = Condition.generate([expected])
+    cond = Condition.generate([expected], 1)
 
     assert cond.fulfillment.to_dict() == expected.to_dict()
 
 
-# TODO FOR CC: see skip reason
-@mark.skip(reason='threshold(hashlock).to_dict() exposes secret')
-def test_generate_threshold_condition_with_hashlock(user_pub, user2_pub,
-                                                    user3_pub):
-    from bigchaindb.common.transaction import Condition
-    from cryptoconditions import (PreimageSha256Fulfillment,
-                                  Ed25519Fulfillment,
-                                  ThresholdSha256Fulfillment)
-
-    secret = b'much secret, wow'
-    hashlock = PreimageSha256Fulfillment(preimage=secret)
-
-    expected_simple1 = Ed25519Fulfillment(public_key=user_pub)
-    expected_simple3 = Ed25519Fulfillment(public_key=user3_pub)
-
-    expected = ThresholdSha256Fulfillment(threshold=2)
-    expected_sub = ThresholdSha256Fulfillment(threshold=2)
-    expected_sub.add_subfulfillment(expected_simple1)
-    expected_sub.add_subfulfillment(hashlock)
-    expected.add_subfulfillment(expected_simple3)
-
-    cond = Condition.generate([[user_pub, hashlock], expected_simple3])
-    assert cond.fulfillment.to_dict() == expected.to_dict()
-
-
 def test_generate_conditions_invalid_parameters(user_pub, user2_pub,
                                                 user3_pub):
     from bigchaindb.common.transaction import Condition
 
     with raises(ValueError):
-        Condition.generate([])
+        Condition.generate([], 1)
     with raises(TypeError):
-        Condition.generate('not a list')
+        Condition.generate('not a list', 1)
     with raises(ValueError):
-        Condition.generate([[user_pub, [user2_pub, [user3_pub]]]])
+        Condition.generate([[user_pub, [user2_pub, [user3_pub]]]], 1)
     with raises(ValueError):
-        Condition.generate([[user_pub]])
+        Condition.generate([[user_pub]], 1)
 
 
 def test_invalid_transaction_initialization():
@@ -321,7 +275,8 @@ def test_invalid_transaction_initialization():
 def test_create_default_asset_on_tx_initialization():
     from bigchaindb.common.transaction import Transaction, Asset
 
-    tx = Transaction(Transaction.CREATE, None)
+    with patch.object(Asset, 'validate_asset', return_value=None):
+        tx = Transaction(Transaction.CREATE, None)
     expected = Asset()
     asset = tx.asset
 
@@ -510,10 +465,72 @@ def test_cast_transaction_link_to_boolean():
     assert bool(TransactionLink(False, False)) is True
 
 
+def test_asset_link_serialization():
+    from bigchaindb.common.transaction import AssetLink
+
+    data_id = 'a asset id'
+    expected = {
+        'id': data_id,
+    }
+    asset_link = AssetLink(data_id)
+
+    assert asset_link.to_dict() == expected
+
+
+def test_asset_link_serialization_with_empty_payload():
+    from bigchaindb.common.transaction import AssetLink
+
+    expected = None
+    asset_link = AssetLink()
+
+    assert asset_link.to_dict() == expected
+
+
+def test_asset_link_deserialization():
+    from bigchaindb.common.transaction import AssetLink
+
+    data_id = 'a asset id'
+    expected = AssetLink(data_id)
+    asset_link = {
+        'id': data_id
+    }
+    asset_link = AssetLink.from_dict(asset_link)
+
+    assert asset_link == expected
+
+
+def test_asset_link_deserialization_with_empty_payload():
+    from bigchaindb.common.transaction import AssetLink
+
+    expected = AssetLink()
+    asset_link = AssetLink.from_dict(None)
+
+    assert asset_link == expected
+
+
+def test_cast_asset_link_to_boolean():
+    from bigchaindb.common.transaction import AssetLink
+
+    assert bool(AssetLink()) is False
+    assert bool(AssetLink('a')) is True
+    assert bool(AssetLink(False)) is True
+
+
+def test_eq_asset_link():
+    from bigchaindb.common.transaction import AssetLink
+
+    asset_id_1 = 'asset_1'
+    asset_id_2 = 'asset_2'
+
+    assert AssetLink(asset_id_1) == AssetLink(asset_id_1)
+    assert AssetLink(asset_id_1) != AssetLink(asset_id_2)
+
+
 def test_add_fulfillment_to_tx(user_ffill):
     from bigchaindb.common.transaction import Transaction, Asset
 
-    tx = Transaction(Transaction.CREATE, Asset(), [], [])
+    with patch.object(Asset, 'validate_asset', return_value=None):
+        tx = Transaction(Transaction.CREATE, Asset(), [], [])
     tx.add_fulfillment(user_ffill)
 
     assert len(tx.fulfillments) == 1
@@ -522,7 +539,8 @@ def test_add_fulfillment_to_tx(user_ffill):
 def test_add_fulfillment_to_tx_with_invalid_parameters():
     from bigchaindb.common.transaction import Transaction, Asset
 
-    tx = Transaction(Transaction.CREATE, Asset())
+    with patch.object(Asset, 'validate_asset', return_value=None):
+        tx = Transaction(Transaction.CREATE, Asset())
     with raises(TypeError):
         tx.add_fulfillment('somewronginput')
 
@@ -530,7 +548,8 @@ def test_add_fulfillment_to_tx_with_invalid_parameters():
 def test_add_condition_to_tx(user_cond):
     from bigchaindb.common.transaction import Transaction, Asset
 
-    tx = Transaction(Transaction.CREATE, Asset())
+    with patch.object(Asset, 'validate_asset', return_value=None):
+        tx = Transaction(Transaction.CREATE, Asset())
     tx.add_condition(user_cond)
 
     assert len(tx.conditions) == 1
@@ -539,7 +558,8 @@ def test_add_condition_to_tx(user_cond):
 def test_add_condition_to_tx_with_invalid_parameters():
     from bigchaindb.common.transaction import Transaction, Asset
 
-    tx = Transaction(Transaction.CREATE, Asset(), [], [])
+    with patch.object(Asset, 'validate_asset', return_value=None):
+        tx = Transaction(Transaction.CREATE, Asset(), [], [])
     with raises(TypeError):
         tx.add_condition('somewronginput')
 
@@ -614,16 +634,14 @@ def test_validate_multiple_fulfillments(user_ffill, user_cond, user_priv):
     from bigchaindb.common.crypto import PrivateKey
     from bigchaindb.common.transaction import Transaction, Asset
 
-    tx = Transaction(Transaction.CREATE, Asset(),
+    tx = Transaction(Transaction.CREATE, Asset(divisible=True),
                      [user_ffill, deepcopy(user_ffill)],
-                     [user_ffill, deepcopy(user_cond)])
+                     [user_cond, deepcopy(user_cond)])
 
     expected_first = deepcopy(tx)
     expected_second = deepcopy(tx)
     expected_first.fulfillments = [expected_first.fulfillments[0]]
-    expected_first.conditions = [expected_first.conditions[0]]
     expected_second.fulfillments = [expected_second.fulfillments[1]]
-    expected_second.conditions = [expected_second.conditions[1]]
 
     expected_first_bytes = str(expected_first).encode()
     expected_first.fulfillments[0].fulfillment.sign(expected_first_bytes,
@@ -674,7 +692,7 @@ def test_multiple_fulfillment_validation_of_transfer_tx(user_ffill, user_cond,
                                                Fulfillment, Condition, Asset)
     from cryptoconditions import Ed25519Fulfillment
 
-    tx = Transaction(Transaction.CREATE, Asset(),
+    tx = Transaction(Transaction.CREATE, Asset(divisible=True),
                      [user_ffill, deepcopy(user_ffill)],
                      [user_cond, deepcopy(user_cond)])
     tx.sign([user_priv])
@@ -715,10 +733,6 @@ def test_validate_fulfillments_of_transfer_tx_with_invalid_params(transfer_tx,
     with raises(TypeError):
         transfer_tx.operation = "Operation that doesn't exist"
         transfer_tx.fulfillments_valid([utx.conditions[0]])
-    with raises(ValueError):
-        tx = utx.sign([user_priv])
-        tx.conditions = []
-        tx.fulfillments_valid()
 
 
 def test_create_create_transaction_single_io(user_cond, user_pub, data,
@@ -754,7 +768,8 @@ def test_create_create_transaction_single_io(user_cond, user_pub, data,
     }
 
     asset = Asset(data, data_id)
-    tx = Transaction.create([user_pub], [user_pub], data, asset).to_dict()
+    tx = Transaction.create([user_pub], [([user_pub], 1)],
+                            data, asset).to_dict()
     tx.pop('id')
     tx['transaction']['metadata'].pop('id')
     tx['transaction'].pop('timestamp')
@@ -766,17 +781,20 @@ def test_create_create_transaction_single_io(user_cond, user_pub, data,
 def test_validate_single_io_create_transaction(user_pub, user_priv, data):
     from bigchaindb.common.transaction import Transaction, Asset
 
-    tx = Transaction.create([user_pub], [user_pub], data, Asset())
+    tx = Transaction.create([user_pub], [([user_pub], 1)], data, Asset())
     tx = tx.sign([user_priv])
     assert tx.fulfillments_valid() is True
 
 
-@mark.skip(reason='Multiple inputs and outputs in CREATE not supported')
-# TODO: Add digital assets
 def test_create_create_transaction_multiple_io(user_cond, user2_cond, user_pub,
                                                user2_pub):
-    from bigchaindb.common.transaction import Transaction
+    from bigchaindb.common.transaction import Transaction, Asset, Fulfillment
 
+    # a fulfillment for a create transaction with multiple `owners_before`
+    # is a fulfillment for an implicit threshold condition with
+    # weight = len(owners_before)
+    ffill = Fulfillment.generate([user_pub, user2_pub]).to_dict()
+    ffill.update({'fid': 0})
     expected = {
         'transaction': {
             'conditions': [user_cond.to_dict(0), user2_cond.to_dict(1)],
@@ -785,45 +803,32 @@ def test_create_create_transaction_multiple_io(user_cond, user2_cond, user_pub,
                     'message': 'hello'
                 }
             },
-            'fulfillments': [
-                {
-                    'owners_before': [
-                        user_pub,
-                    ],
-                    'fid': 0,
-                    'fulfillment': None,
-                    'input': None
-                },
-                {
-                    'owners_before': [
-                        user2_pub,
-                    ],
-                    'fid': 1,
-                    'fulfillment': None,
-                    'input': None
-                }
-            ],
+            'fulfillments': [ffill],
             'operation': 'CREATE',
         },
         'version': 1
     }
-    tx = Transaction.create([user_pub, user2_pub], [user_pub, user2_pub],
-                            {'message': 'hello'}).to_dict()
+    asset = Asset(divisible=True)
+    tx = Transaction.create([user_pub, user2_pub],
+                            [([user_pub], 1), ([user2_pub], 1)],
+                            asset=asset,
+                            metadata={'message': 'hello'}).to_dict()
     tx.pop('id')
     tx['transaction']['metadata'].pop('id')
     tx['transaction'].pop('timestamp')
+    tx['transaction'].pop('asset')
 
     assert tx == expected
 
 
-@mark.skip(reason='Multiple inputs and outputs in CREATE not supported')
-# TODO: Add digital assets
 def test_validate_multiple_io_create_transaction(user_pub, user_priv,
                                                  user2_pub, user2_priv):
-    from bigchaindb.common.transaction import Transaction
+    from bigchaindb.common.transaction import Transaction, Asset
 
-    tx = Transaction.create([user_pub, user2_pub], [user_pub, user2_pub],
-                            {'message': 'hello'})
+    tx = Transaction.create([user_pub, user2_pub],
+                            [([user_pub], 1), ([user2_pub], 1)],
+                            metadata={'message': 'hello'},
+                            asset=Asset(divisible=True))
     tx = tx.sign([user_priv, user2_priv])
     assert tx.fulfillments_valid() is True
 
@@ -862,7 +867,8 @@ def test_create_create_transaction_threshold(user_pub, user2_pub, user3_pub,
         'version': 1
     }
     asset = Asset(data, data_id)
-    tx = Transaction.create([user_pub], [user_pub, user2_pub], data, asset)
+    tx = Transaction.create([user_pub], [([user_pub, user2_pub], 1)],
+                            data, asset)
     tx_dict = tx.to_dict()
     tx_dict.pop('id')
     tx_dict['transaction']['metadata'].pop('id')
@@ -876,80 +882,27 @@ def test_validate_threshold_create_transaction(user_pub, user_priv, user2_pub,
                                                data):
     from bigchaindb.common.transaction import Transaction, Asset
 
-    tx = Transaction.create([user_pub], [user_pub, user2_pub], data, Asset())
+    tx = Transaction.create([user_pub], [([user_pub, user2_pub], 1)],
+                            data, Asset())
     tx = tx.sign([user_priv])
     assert tx.fulfillments_valid() is True
 
 
-def test_create_create_transaction_hashlock(user_pub, data, data_id):
-    from cryptoconditions import PreimageSha256Fulfillment
-    from bigchaindb.common.transaction import Transaction, Condition, Asset
-
-    secret = b'much secret, wow'
-    hashlock = PreimageSha256Fulfillment(preimage=secret).condition_uri
-    cond = Condition(hashlock)
-
-    expected = {
-        'transaction': {
-            'conditions': [cond.to_dict(0)],
-            'metadata': {
-                'data': data,
-            },
-            'asset': {
-                'id': data_id,
-                'divisible': False,
-                'updatable': False,
-                'refillable': False,
-                'data': data,
-            },
-            'fulfillments': [
-                {
-                    'owners_before': [
-                        user_pub,
-                    ],
-                    'fid': 0,
-                    'fulfillment': None,
-                    'input': None
-                },
-            ],
-            'operation': 'CREATE',
-        },
-        'version': 1
-    }
-
-    asset = Asset(data, data_id)
-    tx = Transaction.create([user_pub], [], data, asset, secret).to_dict()
-    tx.pop('id')
-    tx['transaction']['metadata'].pop('id')
-    tx['transaction'].pop('timestamp')
-    tx['transaction']['fulfillments'][0]['fulfillment'] = None
-
-    assert tx == expected
-
-
-def test_validate_hashlock_create_transaction(user_pub, user_priv, data):
-    from bigchaindb.common.transaction import Transaction, Asset
-
-    tx = Transaction.create([user_pub], [], data, Asset(), b'much secret, wow')
-    tx = tx.sign([user_priv])
-    assert tx.fulfillments_valid() is True
-
-
-def test_create_create_transaction_with_invalid_parameters():
+def test_create_create_transaction_with_invalid_parameters(user_pub):
     from bigchaindb.common.transaction import Transaction
 
     with raises(TypeError):
         Transaction.create('not a list')
     with raises(TypeError):
         Transaction.create([], 'not a list')
-    with raises(NotImplementedError):
-        Transaction.create(['a', 'b'], ['c', 'd'])
-    with raises(NotImplementedError):
-        Transaction.create(['a'], [], time_expire=123)
     with raises(ValueError):
-        Transaction.create(['a'], [], secret=None)
+        Transaction.create([], [user_pub])
     with raises(ValueError):
-        Transaction.create([], [], secret='wow, much secret')
+        Transaction.create([user_pub], [])
+    with raises(ValueError):
+        Transaction.create([user_pub], [user_pub])
+    with raises(ValueError):
+        Transaction.create([user_pub], [([user_pub],)])
 
 
 def test_conditions_to_inputs(tx):
@@ -995,7 +948,7 @@ def test_create_transfer_transaction_single_io(tx, user_pub, user2_pub,
     }
     inputs = tx.to_inputs([0])
     asset = Asset(None, data_id)
-    transfer_tx = Transaction.transfer(inputs, [user2_pub], asset=asset)
+    transfer_tx = Transaction.transfer(inputs, [([user2_pub], 1)], asset=asset)
     transfer_tx = transfer_tx.sign([user_priv])
     transfer_tx = transfer_tx.to_dict()
     transfer_tx_body = transfer_tx['transaction']
@@ -1014,16 +967,15 @@ def test_create_transfer_transaction_single_io(tx, user_pub, user2_pub,
     assert transfer_tx.fulfillments_valid([tx.conditions[0]]) is True
 
 
-@mark.skip(reason='FIXME: When divisible assets land')
 def test_create_transfer_transaction_multiple_io(user_pub, user_priv,
                                                  user2_pub, user2_priv,
                                                  user3_pub, user2_cond):
-    from bigchaindb.common.transaction import Transaction
+    from bigchaindb.common.transaction import Transaction, Asset
 
-    tx1 = Transaction.create([user_pub], [user_pub], {'message': 'hello'})
-    tx1 = tx1.sign([user_priv])
-    tx2 = Transaction.create([user2_pub], [user2_pub], {'message': 'hello'})
-    tx2 = tx2.sign([user2_priv])
+    asset = Asset(divisible=True)
+    tx = Transaction.create([user_pub], [([user_pub], 1), ([user2_pub], 1)],
+                            asset=asset, metadata={'message': 'hello'})
+    tx = tx.sign([user_priv])
 
     expected = {
         'transaction': {
@@ -1037,7 +989,7 @@ def test_create_transfer_transaction_multiple_io(user_pub, user_priv,
                     'fid': 0,
                     'fulfillment': None,
                     'input': {
-                        'txid': tx1.id,
+                        'txid': tx.id,
                         'cid': 0
                     }
                 }, {
@@ -1047,8 +999,8 @@ def test_create_transfer_transaction_multiple_io(user_pub, user_priv,
                     'fid': 1,
                     'fulfillment': None,
                     'input': {
-                        'txid': tx2.id,
-                        'cid': 0
+                        'txid': tx.id,
+                        'cid': 1
                     }
                 }
             ],
@@ -1056,30 +1008,28 @@ def test_create_transfer_transaction_multiple_io(user_pub, user_priv,
         },
         'version': 1
     }
-    tx1_inputs = tx1.to_inputs()
-    tx2_inputs = tx2.to_inputs()
-    tx_inputs = tx1_inputs + tx2_inputs
 
-    transfer_tx = Transaction.transfer(tx_inputs, [[user2_pub], [user2_pub]])
+    transfer_tx = Transaction.transfer(tx.to_inputs(),
+                                       [([user2_pub], 1), ([user2_pub], 1)],
+                                       asset=tx.asset)
     transfer_tx = transfer_tx.sign([user_priv, user2_priv])
-    transfer_tx = transfer_tx
 
     assert len(transfer_tx.fulfillments) == 2
     assert len(transfer_tx.conditions) == 2
 
-    combined_conditions = tx1.conditions + tx2.conditions
-    assert transfer_tx.fulfillments_valid(combined_conditions) is True
+    assert transfer_tx.fulfillments_valid(tx.conditions) is True
 
     transfer_tx = transfer_tx.to_dict()
     transfer_tx['transaction']['fulfillments'][0]['fulfillment'] = None
     transfer_tx['transaction']['fulfillments'][1]['fulfillment'] = None
     transfer_tx['transaction'].pop('timestamp')
     transfer_tx.pop('id')
+    transfer_tx['transaction'].pop('asset')
 
     assert expected == transfer_tx
 
 
-def test_create_transfer_with_invalid_parameters():
+def test_create_transfer_with_invalid_parameters(user_pub):
     from bigchaindb.common.transaction import Transaction, Asset
 
     with raises(TypeError):
@@ -1090,17 +1040,25 @@ def test_create_transfer_with_invalid_parameters():
         Transaction.transfer(['fulfillment'], {}, Asset())
     with raises(ValueError):
         Transaction.transfer(['fulfillment'], [], Asset())
+    with raises(ValueError):
+        Transaction.transfer(['fulfillment'], [user_pub], Asset())
+    with raises(ValueError):
+        Transaction.transfer(['fulfillment'], [([user_pub],)], Asset())
 
 
 def test_cant_add_empty_condition():
-    from bigchaindb.common.transaction import Transaction
-    tx = Transaction(Transaction.CREATE, None)
+    from bigchaindb.common.transaction import Transaction, Asset
+
+    with patch.object(Asset, 'validate_asset', return_value=None):
+        tx = Transaction(Transaction.CREATE, None)
     with raises(TypeError):
         tx.add_condition(None)
 
 
 def test_cant_add_empty_fulfillment():
-    from bigchaindb.common.transaction import Transaction
-    tx = Transaction(Transaction.CREATE, None)
+    from bigchaindb.common.transaction import Transaction, Asset
+
+    with patch.object(Asset, 'validate_asset', return_value=None):
+        tx = Transaction(Transaction.CREATE, None)
     with raises(TypeError):
         tx.add_fulfillment(None)
diff --git a/tests/conftest.py b/tests/conftest.py
index 7671cba1..957a5698 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -72,7 +72,7 @@ def b(request, node_config):
 @pytest.fixture
 def create_tx(b, user_pk):
     from bigchaindb.models import Transaction
-    return Transaction.create([b.me], [user_pk])
+    return Transaction.create([b.me], [([user_pk], 1)])
 
 
 @pytest.fixture
@@ -84,5 +84,5 @@ def signed_create_tx(b, create_tx):
 def signed_transfer_tx(signed_create_tx, user_pk, user_sk):
     from bigchaindb.models import Transaction
     inputs = signed_create_tx.to_inputs()
-    tx = Transaction.transfer(inputs, [user_pk], signed_create_tx.asset)
+    tx = Transaction.transfer(inputs, [([user_pk], 1)], signed_create_tx.asset)
     return tx.sign([user_sk])
diff --git a/tests/db/conftest.py b/tests/db/conftest.py
index 219cf068..b04e0a39 100644
--- a/tests/db/conftest.py
+++ b/tests/db/conftest.py
@@ -84,7 +84,7 @@ def inputs(user_pk):
     prev_block_id = g.id
     for block in range(4):
         transactions = [
-            Transaction.create([b.me], [user_pk]).sign([b.me_private])
+            Transaction.create([b.me], [([user_pk], 1)]).sign([b.me_private])
             for i in range(10)
         ]
         block = b.create_block(transactions)
diff --git a/tests/db/test_bigchain_api.py b/tests/db/test_bigchain_api.py
index 1d40ae77..3d1c6151 100644
--- a/tests/db/test_bigchain_api.py
+++ b/tests/db/test_bigchain_api.py
@@ -15,7 +15,7 @@ def dummy_tx():
     import bigchaindb
     from bigchaindb.models import Transaction
     b = bigchaindb.Bigchain()
-    tx = Transaction.create([b.me], [b.me])
+    tx = Transaction.create([b.me], [([b.me], 1)])
     tx = tx.sign([b.me_private])
     return tx
 
@@ -37,7 +37,7 @@ class TestBigchainApi(object):
 
         b.create_genesis_block()
 
-        tx = Transaction.create([b.me], [b.me])
+        tx = Transaction.create([b.me], [([b.me], 1)])
         tx = tx.sign([b.me_private])
         monkeypatch.setattr('time.time', lambda: 1)
         block1 = b.create_block([tx])
@@ -60,7 +60,7 @@ class TestBigchainApi(object):
 
         b.create_genesis_block()
 
-        tx = Transaction.create([b.me], [b.me])
+        tx = Transaction.create([b.me], [([b.me], 1)])
         tx = tx.sign([b.me_private])
         block1 = b.create_block([tx])
 
@@ -74,7 +74,7 @@ class TestBigchainApi(object):
 
         b.create_genesis_block()
 
-        tx = Transaction.create([b.me], [b.me])
+        tx = Transaction.create([b.me], [([b.me], 1)])
         tx = tx.sign([b.me_private])
 
         monkeypatch.setattr('time.time', lambda: 1)
@@ -99,7 +99,7 @@ class TestBigchainApi(object):
 
         b.create_genesis_block()
 
-        tx = Transaction.create([b.me], [b.me])
+        tx = Transaction.create([b.me], [([b.me], 1)])
         tx = tx.sign([b.me_private])
 
         monkeypatch.setattr('time.time', lambda: 1)
@@ -107,13 +107,15 @@ class TestBigchainApi(object):
         b.write_block(block1, durability='hard')
 
         monkeypatch.setattr('time.time', lambda: 2)
-        transfer_tx = Transaction.transfer(tx.to_inputs(), [b.me], tx.asset)
+        transfer_tx = Transaction.transfer(tx.to_inputs(), [([b.me], 1)],
+                                           tx.asset)
         transfer_tx = transfer_tx.sign([b.me_private])
         block2 = b.create_block([transfer_tx])
         b.write_block(block2, durability='hard')
 
         monkeypatch.setattr('time.time', lambda: 3)
-        transfer_tx2 = Transaction.transfer(tx.to_inputs(), [b.me], tx.asset)
+        transfer_tx2 = Transaction.transfer(tx.to_inputs(), [([b.me], 1)],
+                                            tx.asset)
         transfer_tx2 = transfer_tx2.sign([b.me_private])
         block3 = b.create_block([transfer_tx2])
         b.write_block(block3, durability='hard')
@@ -133,7 +135,7 @@ class TestBigchainApi(object):
 
         b.create_genesis_block()
 
-        tx = Transaction.create([b.me], [b.me])
+        tx = Transaction.create([b.me], [([b.me], 1)])
         tx = tx.sign([b.me_private])
 
         monkeypatch.setattr('time.time', lambda: 1)
@@ -159,13 +161,13 @@ class TestBigchainApi(object):
         b.create_genesis_block()
 
         monkeypatch.setattr('time.time', lambda: 1)
-        tx1 = Transaction.create([b.me], [b.me])
+        tx1 = Transaction.create([b.me], [([b.me], 1)])
         tx1 = tx1.sign([b.me_private])
         block1 = b.create_block([tx1])
         b.write_block(block1, durability='hard')
 
         monkeypatch.setattr('time.time', lambda: 2)
-        tx2 = Transaction.create([b.me], [b.me])
+        tx2 = Transaction.create([b.me], [([b.me], 1)])
         tx2 = tx2.sign([b.me_private])
         block2 = b.create_block([tx2])
         b.write_block(block2, durability='hard')
@@ -185,7 +187,7 @@ class TestBigchainApi(object):
         from bigchaindb.models import Transaction
 
         metadata = {'msg': 'Hello BigchainDB!'}
-        tx = Transaction.create([b.me], [user_pk], metadata=metadata)
+        tx = Transaction.create([b.me], [([user_pk], 1)], metadata=metadata)
 
         block = b.create_block([tx])
         b.write_block(block, durability='hard')
@@ -205,7 +207,7 @@ class TestBigchainApi(object):
         input_tx = b.get_owned_ids(user_pk).pop()
         input_tx = b.get_transaction(input_tx.txid)
         inputs = input_tx.to_inputs()
-        tx = Transaction.transfer(inputs, [user_pk], input_tx.asset)
+        tx = Transaction.transfer(inputs, [([user_pk], 1)], input_tx.asset)
         tx = tx.sign([user_sk])
         response = b.write_transaction(tx)
 
@@ -223,7 +225,7 @@ class TestBigchainApi(object):
         input_tx = b.get_owned_ids(user_pk).pop()
         input_tx = b.get_transaction(input_tx.txid)
         inputs = input_tx.to_inputs()
-        tx = Transaction.transfer(inputs, [user_pk], input_tx.asset)
+        tx = Transaction.transfer(inputs, [([user_pk], 1)], input_tx.asset)
         tx = tx.sign([user_sk])
         b.write_transaction(tx)
 
@@ -243,7 +245,7 @@ class TestBigchainApi(object):
         input_tx = b.get_owned_ids(user_pk).pop()
         input_tx = b.get_transaction(input_tx.txid)
         inputs = input_tx.to_inputs()
-        tx = Transaction.transfer(inputs, [user_pk], input_tx.asset)
+        tx = Transaction.transfer(inputs, [([user_pk], 1)], input_tx.asset)
         tx = tx.sign([user_sk])
         # There's no need to b.write_transaction(tx) to the backlog
 
@@ -267,7 +269,7 @@ class TestBigchainApi(object):
         input_tx = b.get_owned_ids(user_pk).pop()
         input_tx = b.get_transaction(input_tx.txid)
         inputs = input_tx.to_inputs()
-        tx = Transaction.transfer(inputs, [user_pk], input_tx.asset)
+        tx = Transaction.transfer(inputs, [([user_pk], 1)], input_tx.asset)
         tx = tx.sign([user_sk])
 
         # Make sure there's a copy of tx in the backlog
@@ -369,6 +371,15 @@ class TestBigchainApi(object):
 
         assert excinfo.value.args[0] == 'Empty block creation is not allowed'
 
+    @pytest.mark.usefixtures('inputs')
+    def test_get_block_by_id(self, b):
+        new_block = dummy_block()
+        b.write_block(new_block, durability='hard')
+
+        assert b.get_block(new_block.id) == new_block.to_dict()
+        block, status = b.get_block(new_block.id, include_status=True)
+        assert status == b.BLOCK_UNDECIDED
+
     def test_get_last_voted_block_returns_genesis_if_no_votes_has_been_casted(self, b):
         import rethinkdb as r
         from bigchaindb import util
@@ -528,7 +539,7 @@ class TestBigchainApi(object):
         input_tx = b.get_owned_ids(user_pk).pop()
         input_tx = b.get_transaction(input_tx.txid)
         inputs = input_tx.to_inputs()
-        tx = Transaction.transfer(inputs, [user_pk], input_tx.asset)
+        tx = Transaction.transfer(inputs, [([user_pk], 1)], input_tx.asset)
         tx = tx.sign([user_sk])
         b.write_transaction(tx)
 
@@ -554,7 +565,7 @@ class TestBigchainApi(object):
             input_tx = b.get_owned_ids(user_pk).pop()
             input_tx = b.get_transaction(input_tx.txid)
             inputs = input_tx.to_inputs()
-            tx = Transaction.transfer(inputs, [user_pk], input_tx.asset)
+            tx = Transaction.transfer(inputs, [([user_pk], 1)], input_tx.asset)
             tx = tx.sign([user_sk])
             b.write_transaction(tx)
 
@@ -578,11 +589,21 @@ class TestBigchainApi(object):
         fulfillment = Fulfillment(Ed25519Fulfillment(public_key=user_pk),
                                   [user_pk],
                                   TransactionLink('somethingsomething', 0))
-        tx = Transaction.transfer([fulfillment], [user_pk], Asset())
+        tx = Transaction.transfer([fulfillment], [([user_pk], 1)], Asset())
 
-        with pytest.raises(TransactionDoesNotExist) as excinfo:
+        with pytest.raises(TransactionDoesNotExist):
             tx.validate(Bigchain())
 
+    def test_count_backlog(self, b, user_vk):
+        from bigchaindb.models import Transaction
+
+        for _ in range(4):
+            tx = Transaction.create([b.me],
+                                    [([user_vk], 1)]).sign([b.me_private])
+            b.write_transaction(tx)
+
+        assert b.backend.count_backlog() == 4
+
 
 class TestTransactionValidation(object):
     def test_create_operation_with_inputs(self, b, user_pk, create_tx):
@@ -620,7 +641,7 @@ class TestTransactionValidation(object):
         input_tx = b.get_owned_ids(user_pk).pop()
         input_transaction = b.get_transaction(input_tx.txid)
         sk, pk = generate_key_pair()
-        tx = Transaction.create([pk], [user_pk])
+        tx = Transaction.create([pk], [([user_pk], 1)])
         tx.operation = 'TRANSFER'
         tx.asset = input_transaction.asset
         tx.fulfillments[0].tx_input = input_tx
@@ -664,7 +685,8 @@ class TestTransactionValidation(object):
         input_tx = b.get_owned_ids(user_pk).pop()
         input_tx = b.get_transaction(input_tx.txid)
         inputs = input_tx.to_inputs()
-        transfer_tx = Transaction.transfer(inputs, [user_pk], input_tx.asset)
+        transfer_tx = Transaction.transfer(inputs, [([user_pk], 1)],
+                                           input_tx.asset)
         transfer_tx = transfer_tx.sign([user_sk])
 
         assert transfer_tx == b.validate_transaction(transfer_tx)
@@ -679,16 +701,17 @@ class TestTransactionValidation(object):
         assert transfer_tx == b.validate_transaction(transfer_tx)
 
     @pytest.mark.usefixtures('inputs')
-    def test_fulfillment_not_in_valid_block(self, b, user_pk, user_sk):
+    def test_transaction_not_in_valid_block(self, b, user_pk, user_sk):
         from bigchaindb.models import Transaction
-        from bigchaindb.common.exceptions import FulfillmentNotInValidBlock
+        from bigchaindb.common.exceptions import TransactionNotInValidBlock
 
         input_tx = b.get_owned_ids(user_pk).pop()
         input_tx = b.get_transaction(input_tx.txid)
         inputs = input_tx.to_inputs()
 
         # create a transaction that's valid but not in a voted valid block
-        transfer_tx = Transaction.transfer(inputs, [user_pk], input_tx.asset)
+        transfer_tx = Transaction.transfer(inputs, [([user_pk], 1)],
+                                           input_tx.asset)
         transfer_tx = transfer_tx.sign([user_sk])
 
         assert transfer_tx == b.validate_transaction(transfer_tx)
@@ -698,11 +721,12 @@ class TestTransactionValidation(object):
         b.write_block(block, durability='hard')
 
         # create transaction with the undecided input
-        tx_invalid = Transaction.transfer(transfer_tx.to_inputs(), [user_pk],
-                                         transfer_tx.asset)
+        tx_invalid = Transaction.transfer(transfer_tx.to_inputs(),
+                                          [([user_pk], 1)],
+                                          transfer_tx.asset)
         tx_invalid = tx_invalid.sign([user_sk])
 
-        with pytest.raises(FulfillmentNotInValidBlock):
+        with pytest.raises(TransactionNotInValidBlock):
             b.validate_transaction(tx_invalid)
 
 
@@ -797,7 +821,7 @@ class TestMultipleInputs(object):
         tx_link = b.get_owned_ids(user_pk).pop()
         input_tx = b.get_transaction(tx_link.txid)
         inputs = input_tx.to_inputs()
-        tx = Transaction.transfer(inputs, [user2_pk], input_tx.asset)
+        tx = Transaction.transfer(inputs, [([user2_pk], 1)], input_tx.asset)
         tx = tx.sign([user_sk])
 
         # validate transaction
@@ -805,69 +829,6 @@ class TestMultipleInputs(object):
         assert len(tx.fulfillments) == 1
         assert len(tx.conditions) == 1
 
-    @pytest.mark.skipif(reason=('Multiple inputs are only allowed for the '
-                                'same asset. Remove this after implementing ',
-                                'multiple assets'))
-    @pytest.mark.usefixtures('inputs')
-    def test_transfer_single_owners_multiple_inputs(self, b, user_sk, user_pk):
-        from bigchaindb.common import crypto
-        from bigchaindb.models import Transaction
-
-        user2_sk, user2_pk = crypto.generate_key_pair()
-
-        # get inputs
-        owned_inputs = b.get_owned_ids(user_pk)
-        input_txs = [b.get_transaction(tx_link.txid) for tx_link
-                     in owned_inputs]
-        inputs = sum([input_tx.to_inputs() for input_tx in input_txs], [])
-        tx = Transaction.transfer(inputs, len(inputs) * [[user_pk]])
-        tx = tx.sign([user_sk])
-        assert b.validate_transaction(tx) == tx
-        assert len(tx.fulfillments) == len(inputs)
-        assert len(tx.conditions) == len(inputs)
-
-    @pytest.mark.skipif(reason=('Multiple inputs are only allowed for the '
-                                'same asset. Remove this after implementing ',
-                                'multiple assets'))
-    @pytest.mark.usefixtures('inputs')
-    def test_transfer_single_owners_single_input_from_multiple_outputs(self, b,
-                                                                       user_sk,
-                                                                       user_pk):
-        from bigchaindb.common import crypto
-        from bigchaindb.models import Transaction
-
-        user2_sk, user2_pk = crypto.generate_key_pair()
-
-        # get inputs
-        owned_inputs = b.get_owned_ids(user_pk)
-        input_txs = [b.get_transaction(tx_link.txid) for tx_link
-                     in owned_inputs]
-        inputs = sum([input_tx.to_inputs() for input_tx in input_txs], [])
-        tx = Transaction.transfer(inputs, len(inputs) * [[user2_pk]])
-        tx = tx.sign([user_sk])
-
-        # create block with the transaction
-        block = b.create_block([tx])
-        b.write_block(block, durability='hard')
-
-        # vote block valid
-        vote = b.vote(block.id, b.get_last_voted_block().id, True)
-        b.write_vote(vote)
-
-        # get inputs from user2
-        owned_inputs = b.get_owned_ids(user2_pk)
-        assert len(owned_inputs) == len(inputs)
-
-        # create a transaction with a single input from a multiple output transaction
-        tx_link = owned_inputs.pop()
-        inputs = b.get_transaction(tx_link.txid).to_inputs([0])
-        tx = Transaction.transfer(inputs, [user_pk])
-        tx = tx.sign([user2_sk])
-
-        assert b.is_valid_transaction(tx) == tx
-        assert len(tx.fulfillments) == 1
-        assert len(tx.conditions) == 1
-
     def test_single_owner_before_multiple_owners_after_single_input(self, b,
                                                                     user_sk,
                                                                     user_pk,
@@ -881,47 +842,14 @@ class TestMultipleInputs(object):
         owned_inputs = b.get_owned_ids(user_pk)
         tx_link = owned_inputs.pop()
         input_tx = b.get_transaction(tx_link.txid)
-        tx = Transaction.transfer(input_tx.to_inputs(), [[user2_pk, user3_pk]], input_tx.asset)
+        tx = Transaction.transfer(input_tx.to_inputs(),
+                                  [([user2_pk, user3_pk], 1)], input_tx.asset)
         tx = tx.sign([user_sk])
 
         assert b.is_valid_transaction(tx) == tx
         assert len(tx.fulfillments) == 1
         assert len(tx.conditions) == 1
 
-    @pytest.mark.skipif(reason=('Multiple inputs are only allowed for the '
-                                'same asset. Remove this after implementing ',
-                                'multiple assets'))
-    @pytest.mark.usefixtures('inputs')
-    def test_single_owner_before_multiple_owners_after_multiple_inputs(self, b,
-                                                                       user_sk,
-                                                                       user_pk):
-        from bigchaindb.common import crypto
-        from bigchaindb.models import Transaction
-
-        user2_sk, user2_pk = crypto.generate_key_pair()
-        user3_sk, user3_pk = crypto.generate_key_pair()
-
-        owned_inputs = b.get_owned_ids(user_pk)
-        input_txs = [b.get_transaction(tx_link.txid) for tx_link
-                     in owned_inputs]
-        inputs = sum([input_tx.to_inputs() for input_tx in input_txs], [])
-
-        tx = Transaction.transfer(inputs, len(inputs) * [[user2_pk, user3_pk]])
-        tx = tx.sign([user_sk])
-
-        # create block with the transaction
-        block = b.create_block([tx])
-        b.write_block(block, durability='hard')
-
-        # vote block valid
-        vote = b.vote(block.id, b.get_last_voted_block().id, True)
-        b.write_vote(vote)
-
-        # validate transaction
-        assert b.is_valid_transaction(tx) == tx
-        assert len(tx.fulfillments) == len(inputs)
-        assert len(tx.conditions) == len(inputs)
-
     @pytest.mark.usefixtures('inputs')
     def test_multiple_owners_before_single_owner_after_single_input(self, b,
                                                                     user_sk,
@@ -932,7 +860,7 @@ class TestMultipleInputs(object):
         user2_sk, user2_pk = crypto.generate_key_pair()
         user3_sk, user3_pk = crypto.generate_key_pair()
 
-        tx = Transaction.create([b.me], [user_pk, user2_pk])
+        tx = Transaction.create([b.me], [([user_pk, user2_pk], 1)])
         tx = tx.sign([b.me_private])
         block = b.create_block([tx])
         b.write_block(block, durability='hard')
@@ -945,7 +873,8 @@ class TestMultipleInputs(object):
         input_tx = b.get_transaction(owned_input.txid)
         inputs = input_tx.to_inputs()
 
-        transfer_tx = Transaction.transfer(inputs, [user3_pk], input_tx.asset)
+        transfer_tx = Transaction.transfer(inputs, [([user3_pk], 1)],
+                                           input_tx.asset)
         transfer_tx = transfer_tx.sign([user_sk, user2_sk])
 
         # validate transaction
@@ -953,29 +882,6 @@ class TestMultipleInputs(object):
         assert len(transfer_tx.fulfillments) == 1
         assert len(transfer_tx.conditions) == 1
 
-    @pytest.mark.skipif(reason=('Multiple inputs are only allowed for the '
-                                'same asset. Remove this after implementing ',
-                                'multiple assets'))
-    @pytest.mark.usefixtures('inputs_shared')
-    def test_multiple_owners_before_single_owner_after_multiple_inputs(self, b,
-                                          user_sk, user_pk, user2_pk, user2_sk):
-        from bigchaindb.common import crypto
-        from bigchaindb.models import Transaction
-
-        # create a new users
-        user3_sk, user3_pk = crypto.generate_key_pair()
-
-        tx_links = b.get_owned_ids(user_pk)
-        inputs = sum([b.get_transaction(tx_link.txid).to_inputs() for tx_link
-                      in tx_links], [])
-
-        tx = Transaction.transfer(inputs, len(inputs) * [[user3_pk]])
-        tx = tx.sign([user_sk, user2_sk])
-
-        assert b.is_valid_transaction(tx) == tx
-        assert len(tx.fulfillments) == len(inputs)
-        assert len(tx.conditions) == len(inputs)
-
     @pytest.mark.usefixtures('inputs')
     def test_multiple_owners_before_multiple_owners_after_single_input(self, b,
                                                                        user_sk,
@@ -987,7 +893,7 @@ class TestMultipleInputs(object):
         user3_sk, user3_pk = crypto.generate_key_pair()
         user4_sk, user4_pk = crypto.generate_key_pair()
 
-        tx = Transaction.create([b.me], [user_pk, user2_pk])
+        tx = Transaction.create([b.me], [([user_pk, user2_pk], 1)])
         tx = tx.sign([b.me_private])
         block = b.create_block([tx])
         b.write_block(block, durability='hard')
@@ -1000,38 +906,14 @@ class TestMultipleInputs(object):
         tx_link = b.get_owned_ids(user_pk).pop()
         tx_input = b.get_transaction(tx_link.txid)
 
-        tx = Transaction.transfer(tx_input.to_inputs(), [[user3_pk, user4_pk]], tx_input.asset)
+        tx = Transaction.transfer(tx_input.to_inputs(),
+                                  [([user3_pk, user4_pk], 1)], tx_input.asset)
         tx = tx.sign([user_sk, user2_sk])
 
         assert b.is_valid_transaction(tx) == tx
         assert len(tx.fulfillments) == 1
         assert len(tx.conditions) == 1
 
-    @pytest.mark.skipif(reason=('Multiple inputs are only allowed for the '
-                                'same asset. Remove this after implementing ',
-                                'multiple assets'))
-    @pytest.mark.usefixtures('inputs_shared')
-    def test_multiple_owners_before_multiple_owners_after_multiple_inputs(self, b,
-                                                                user_sk, user_pk,
-                                                                user2_sk, user2_pk):
-        from bigchaindb.common import crypto
-        from bigchaindb.models import Transaction
-
-        # create a new users
-        user3_sk, user3_pk = crypto.generate_key_pair()
-        user4_sk, user4_pk = crypto.generate_key_pair()
-
-        tx_links = b.get_owned_ids(user_pk)
-        inputs = sum([b.get_transaction(tx_link.txid).to_inputs() for tx_link
-                      in tx_links], [])
-
-        tx = Transaction.transfer(inputs, len(inputs) * [[user3_pk, user4_pk]])
-        tx = tx.sign([user_sk, user2_sk])
-
-        assert b.is_valid_transaction(tx) == tx
-        assert len(tx.fulfillments) == len(inputs)
-        assert len(tx.conditions) == len(inputs)
-
     def test_get_owned_ids_single_tx_single_output(self, b, user_sk, user_pk):
         from bigchaindb.common import crypto
         from bigchaindb.common.transaction import TransactionLink
@@ -1039,7 +921,7 @@ class TestMultipleInputs(object):
 
         user2_sk, user2_pk = crypto.generate_key_pair()
 
-        tx = Transaction.create([b.me], [user_pk])
+        tx = Transaction.create([b.me], [([user_pk], 1)])
         tx = tx.sign([b.me_private])
         block = b.create_block([tx])
         b.write_block(block, durability='hard')
@@ -1049,7 +931,7 @@ class TestMultipleInputs(object):
         assert owned_inputs_user1 == [TransactionLink(tx.id, 0)]
         assert owned_inputs_user2 == []
 
-        tx = Transaction.transfer(tx.to_inputs(), [user2_pk], tx.asset)
+        tx = Transaction.transfer(tx.to_inputs(), [([user2_pk], 1)], tx.asset)
         tx = tx.sign([user_sk])
         block = b.create_block([tx])
         b.write_block(block, durability='hard')
@@ -1069,7 +951,7 @@ class TestMultipleInputs(object):
         genesis = b.create_genesis_block()
         user2_sk, user2_pk = crypto.generate_key_pair()
 
-        tx = Transaction.create([b.me], [user_pk])
+        tx = Transaction.create([b.me], [([user_pk], 1)])
         tx = tx.sign([b.me_private])
         block = b.create_block([tx])
         b.write_block(block, durability='hard')
@@ -1085,7 +967,8 @@ class TestMultipleInputs(object):
 
         # NOTE: The transaction itself is valid, still will mark the block
         #       as invalid to mock the behavior.
-        tx_invalid = Transaction.transfer(tx.to_inputs(), [user2_pk], tx.asset)
+        tx_invalid = Transaction.transfer(tx.to_inputs(), [([user2_pk], 1)],
+                                          tx.asset)
         tx_invalid = tx_invalid.sign([user_sk])
         block = b.create_block([tx_invalid])
         b.write_block(block, durability='hard')
@@ -1101,47 +984,45 @@ class TestMultipleInputs(object):
         assert owned_inputs_user1 == [TransactionLink(tx.id, 0)]
         assert owned_inputs_user2 == []
 
-    @pytest.mark.skipif(reason=('Multiple inputs are only allowed for the '
-                                'same asset. Remove this after implementing ',
-                                'multiple assets'))
     def test_get_owned_ids_single_tx_multiple_outputs(self, b, user_sk,
                                                       user_pk):
-        import random
         from bigchaindb.common import crypto
-        from bigchaindb.common.transaction import TransactionLink
+        from bigchaindb.common.transaction import TransactionLink, Asset
         from bigchaindb.models import Transaction
 
         user2_sk, user2_pk = crypto.generate_key_pair()
 
-        transactions = []
-        for i in range(2):
-            payload = {'somedata': random.randint(0, 255)}
-            tx = Transaction.create([b.me], [user_pk], payload)
-            tx = tx.sign([b.me_private])
-            transactions.append(tx)
-        block = b.create_block(transactions)
+        # create divisible asset
+        asset = Asset(divisible=True)
+        tx_create = Transaction.create([b.me],
+                                       [([user_pk], 1), ([user_pk], 1)],
+                                       asset=asset)
+        tx_create_signed = tx_create.sign([b.me_private])
+        block = b.create_block([tx_create_signed])
         b.write_block(block, durability='hard')
 
         # get input
         owned_inputs_user1 = b.get_owned_ids(user_pk)
         owned_inputs_user2 = b.get_owned_ids(user2_pk)
 
-        expected_owned_inputs_user1 = [TransactionLink(tx.id, 0) for tx
-                                       in transactions]
+        expected_owned_inputs_user1 = [TransactionLink(tx_create.id, 0),
+                                       TransactionLink(tx_create.id, 1)]
         assert owned_inputs_user1 == expected_owned_inputs_user1
         assert owned_inputs_user2 == []
 
-        inputs = sum([tx.to_inputs() for tx in transactions], [])
-        tx = Transaction.transfer(inputs, len(inputs) * [[user2_pk]])
-        tx = tx.sign([user_sk])
-        block = b.create_block([tx])
+        # transfer divisible asset divided in two outputs
+        tx_transfer = Transaction.transfer(tx_create.to_inputs(),
+                                           [([user2_pk], 1), ([user2_pk], 1)],
+                                           asset=tx_create.asset)
+        tx_transfer_signed = tx_transfer.sign([user_sk])
+        block = b.create_block([tx_transfer_signed])
         b.write_block(block, durability='hard')
 
         owned_inputs_user1 = b.get_owned_ids(user_pk)
         owned_inputs_user2 = b.get_owned_ids(user2_pk)
         assert owned_inputs_user1 == []
-        assert owned_inputs_user2 == [TransactionLink(tx.id, 0),
-                                      TransactionLink(tx.id, 1)]
+        assert owned_inputs_user2 == [TransactionLink(tx_transfer.id, 0),
+                                      TransactionLink(tx_transfer.id, 1)]
 
     def test_get_owned_ids_multiple_owners(self, b, user_sk, user_pk):
         from bigchaindb.common import crypto
@@ -1151,7 +1032,7 @@ class TestMultipleInputs(object):
         user2_sk, user2_pk = crypto.generate_key_pair()
         user3_sk, user3_pk = crypto.generate_key_pair()
 
-        tx = Transaction.create([b.me], [user_pk, user2_pk])
+        tx = Transaction.create([b.me], [([user_pk, user2_pk], 1)])
         tx = tx.sign([b.me_private])
         block = b.create_block([tx])
         b.write_block(block, durability='hard')
@@ -1163,7 +1044,7 @@ class TestMultipleInputs(object):
         assert owned_inputs_user1 == owned_inputs_user2
         assert owned_inputs_user1 == expected_owned_inputs_user1
 
-        tx = Transaction.transfer(tx.to_inputs(), [user3_pk], tx.asset)
+        tx = Transaction.transfer(tx.to_inputs(), [([user3_pk], 1)], tx.asset)
         tx = tx.sign([user_sk, user2_sk])
         block = b.create_block([tx])
         b.write_block(block, durability='hard')
@@ -1179,7 +1060,7 @@ class TestMultipleInputs(object):
 
         user2_sk, user2_pk = crypto.generate_key_pair()
 
-        tx = Transaction.create([b.me], [user_pk])
+        tx = Transaction.create([b.me], [([user_pk], 1)])
         tx = tx.sign([b.me_private])
         block = b.create_block([tx])
         b.write_block(block, durability='hard')
@@ -1193,7 +1074,7 @@ class TestMultipleInputs(object):
         assert spent_inputs_user1 is None
 
         # create a transaction and block
-        tx = Transaction.transfer(tx.to_inputs(), [user2_pk], tx.asset)
+        tx = Transaction.transfer(tx.to_inputs(), [([user2_pk], 1)], tx.asset)
         tx = tx.sign([user_sk])
         block = b.create_block([tx])
         b.write_block(block, durability='hard')
@@ -1210,7 +1091,7 @@ class TestMultipleInputs(object):
         # create a new users
         user2_sk, user2_pk = crypto.generate_key_pair()
 
-        tx = Transaction.create([b.me], [user_pk])
+        tx = Transaction.create([b.me], [([user_pk], 1)])
         tx = tx.sign([b.me_private])
         block = b.create_block([tx])
         b.write_block(block, durability='hard')
@@ -1228,7 +1109,7 @@ class TestMultipleInputs(object):
         assert spent_inputs_user1 is None
 
         # create a transaction and block
-        tx = Transaction.transfer(tx.to_inputs(), [user2_pk], tx.asset)
+        tx = Transaction.transfer(tx.to_inputs(), [([user2_pk], 1)], tx.asset)
         tx = tx.sign([user_sk])
         block = b.create_block([tx])
         b.write_block(block, durability='hard')
@@ -1243,24 +1124,23 @@ class TestMultipleInputs(object):
         # Now there should be no spents (the block is invalid)
         assert spent_inputs_user1 is None
 
-    @pytest.mark.skipif(reason=('Multiple inputs are only allowed for the '
-                                'same asset. Remove this after implementing ',
-                                'multiple assets'))
     def test_get_spent_single_tx_multiple_outputs(self, b, user_sk, user_pk):
-        import random
         from bigchaindb.common import crypto
         from bigchaindb.models import Transaction
+        from bigchaindb.common.transaction import Asset
 
         # create a new users
         user2_sk, user2_pk = crypto.generate_key_pair()
 
-        transactions = []
-        for i in range(3):
-            payload = {'somedata': random.randint(0, 255)}
-            tx = Transaction.create([b.me], [user_pk], payload)
-            tx = tx.sign([b.me_private])
-            transactions.append(tx)
-        block = b.create_block(transactions)
+        # create a divisible asset with 3 outputs
+        asset = Asset(divisible=True)
+        tx_create = Transaction.create([b.me],
+                                       [([user_pk], 1),
+                                        ([user_pk], 1),
+                                        ([user_pk], 1)],
+                                       asset=asset)
+        tx_create_signed = tx_create.sign([b.me_private])
+        block = b.create_block([tx_create_signed])
         b.write_block(block, durability='hard')
 
         owned_inputs_user1 = b.get_owned_ids(user_pk)
@@ -1269,22 +1149,22 @@ class TestMultipleInputs(object):
         for input_tx in owned_inputs_user1:
             assert b.get_spent(input_tx.txid, input_tx.cid) is None
 
-        # select inputs to use
-        inputs = sum([tx.to_inputs() for tx in transactions[:2]], [])
-
-        # create a transaction and block
-        tx = Transaction.transfer(inputs, len(inputs) * [[user2_pk]])
-        tx = tx.sign([user_sk])
-        block = b.create_block([tx])
+        # transfer the first 2 inputs
+        tx_transfer = Transaction.transfer(tx_create.to_inputs()[:2],
+                                           [([user2_pk], 1), ([user2_pk], 1)],
+                                           asset=tx_create.asset)
+        tx_transfer_signed = tx_transfer.sign([user_sk])
+        block = b.create_block([tx_transfer_signed])
         b.write_block(block, durability='hard')
 
         # check that used inputs are marked as spent
-        for ffill in inputs:
-            assert b.get_spent(ffill.tx_input.txid, ffill.tx_input.cid) == tx
+        for ffill in tx_create.to_inputs()[:2]:
+            spent_tx = b.get_spent(ffill.tx_input.txid, ffill.tx_input.cid)
+            assert spent_tx == tx_transfer_signed
 
         # check if remaining transaction that was unspent is also perceived
         # spendable by BigchainDB
-        assert b.get_spent(transactions[2].id, 0) is None
+        assert b.get_spent(tx_create.to_inputs()[2].tx_input.txid, 2) is None
 
     def test_get_spent_multiple_owners(self, b, user_sk, user_pk):
         import random
@@ -1297,7 +1177,8 @@ class TestMultipleInputs(object):
         transactions = []
         for i in range(3):
             payload = {'somedata': random.randint(0, 255)}
-            tx = Transaction.create([b.me], [user_pk, user2_pk], payload)
+            tx = Transaction.create([b.me], [([user_pk, user2_pk], 1)],
+                                    payload)
             tx = tx.sign([b.me_private])
             transactions.append(tx)
         block = b.create_block(transactions)
@@ -1310,7 +1191,8 @@ class TestMultipleInputs(object):
             assert b.get_spent(input_tx.txid, input_tx.cid) is None
 
         # create a transaction
-        tx = Transaction.transfer(transactions[0].to_inputs(), [user3_pk], transactions[0].asset)
+        tx = Transaction.transfer(transactions[0].to_inputs(),
+                                  [([user3_pk], 1)], transactions[0].asset)
         tx = tx.sign([user_sk, user2_sk])
         block = b.create_block([tx])
         b.write_block(block, durability='hard')
diff --git a/tests/pipelines/test_block_creation.py b/tests/pipelines/test_block_creation.py
index b2c2c9a5..db46a758 100644
--- a/tests/pipelines/test_block_creation.py
+++ b/tests/pipelines/test_block_creation.py
@@ -45,7 +45,7 @@ def test_create_block(b, user_pk):
     block_maker = BlockPipeline()
 
     for i in range(100):
-        tx = Transaction.create([b.me], [user_pk])
+        tx = Transaction.create([b.me], [([user_pk], 1)])
         tx = tx.sign([b.me_private])
         block_maker.create(tx)
 
@@ -63,7 +63,7 @@ def test_write_block(b, user_pk):
 
     txs = []
     for i in range(100):
-        tx = Transaction.create([b.me], [user_pk])
+        tx = Transaction.create([b.me], [([user_pk], 1)])
         tx = tx.sign([b.me_private])
         txs.append(tx)
 
@@ -82,7 +82,7 @@ def test_duplicate_transaction(b, user_pk):
 
     txs = []
     for i in range(10):
-        tx = Transaction.create([b.me], [user_pk])
+        tx = Transaction.create([b.me], [([user_pk], 1)])
         tx = tx.sign([b.me_private])
         txs.append(tx)
 
@@ -109,7 +109,7 @@ def test_delete_tx(b, user_pk):
     from bigchaindb.pipelines.block import BlockPipeline
     block_maker = BlockPipeline()
     for i in range(100):
-        tx = Transaction.create([b.me], [user_pk])
+        tx = Transaction.create([b.me], [([user_pk], 1)])
         tx = tx.sign([b.me_private])
         block_maker.create(tx)
         # make sure the tx appears in the backlog
@@ -138,7 +138,8 @@ def test_prefeed(b, user_pk):
     from bigchaindb.pipelines.block import initial
 
     for i in range(100):
-        tx = Transaction.create([b.me], [user_pk], {'msg': random.random()})
+        tx = Transaction.create([b.me], [([user_pk], 1)],
+                                {'msg': random.random()})
         tx = tx.sign([b.me_private])
         b.write_transaction(tx)
 
@@ -167,7 +168,8 @@ def test_full_pipeline(b, user_pk):
 
     count_assigned_to_me = 0
     for i in range(100):
-        tx = Transaction.create([b.me], [user_pk], {'msg': random.random()})
+        tx = Transaction.create([b.me], [([user_pk], 1)],
+                                {'msg': random.random()})
         tx = tx.sign([b.me_private]).to_dict()
         assignee = random.choice([b.me, 'aaa', 'bbb', 'ccc'])
         tx['assignee'] = assignee
diff --git a/tests/pipelines/test_election.py b/tests/pipelines/test_election.py
index 53e7226a..f0d57e1b 100644
--- a/tests/pipelines/test_election.py
+++ b/tests/pipelines/test_election.py
@@ -15,7 +15,7 @@ def test_check_for_quorum_invalid(b, user_pk):
     e = election.Election()
 
     # create blocks with transactions
-    tx1 = Transaction.create([b.me], [user_pk])
+    tx1 = Transaction.create([b.me], [([user_pk], 1)])
     test_block = b.create_block([tx1])
 
     # simulate a federation with four voters
@@ -44,7 +44,7 @@ def test_check_for_quorum_invalid_prev_node(b, user_pk):
     e = election.Election()
 
     # create blocks with transactions
-    tx1 = Transaction.create([b.me], [user_pk])
+    tx1 = Transaction.create([b.me], [([user_pk], 1)])
     test_block = b.create_block([tx1])
 
     # simulate a federation with four voters
@@ -74,7 +74,7 @@ def test_check_for_quorum_valid(b, user_pk):
     e = election.Election()
 
     # create blocks with transactions
-    tx1 = Transaction.create([b.me], [user_pk])
+    tx1 = Transaction.create([b.me], [([user_pk], 1)])
     test_block = b.create_block([tx1])
 
     # simulate a federation with four voters
@@ -103,7 +103,7 @@ def test_check_requeue_transaction(b, user_pk):
     e = election.Election()
 
     # create blocks with transactions
-    tx1 = Transaction.create([b.me], [user_pk])
+    tx1 = Transaction.create([b.me], [([user_pk], 1)])
     test_block = b.create_block([tx1])
 
     e.requeue_transactions(test_block)
@@ -131,7 +131,8 @@ def test_full_pipeline(b, user_pk):
     # write two blocks
     txs = []
     for i in range(100):
-        tx = Transaction.create([b.me], [user_pk], {'msg': random.random()})
+        tx = Transaction.create([b.me], [([user_pk], 1)],
+                                {'msg': random.random()})
         tx = tx.sign([b.me_private])
         txs.append(tx)
 
@@ -140,7 +141,8 @@ def test_full_pipeline(b, user_pk):
 
     txs = []
     for i in range(100):
-        tx = Transaction.create([b.me], [user_pk], {'msg': random.random()})
+        tx = Transaction.create([b.me], [([user_pk], 1)],
+                                {'msg': random.random()})
         tx = tx.sign([b.me_private])
         txs.append(tx)
 
diff --git a/tests/pipelines/test_stale_monitor.py b/tests/pipelines/test_stale_monitor.py
index 1e033382..eb260ffe 100644
--- a/tests/pipelines/test_stale_monitor.py
+++ b/tests/pipelines/test_stale_monitor.py
@@ -10,7 +10,7 @@ import os
 
 def test_get_stale(b, user_pk):
     from bigchaindb.models import Transaction
-    tx = Transaction.create([b.me], [user_pk])
+    tx = Transaction.create([b.me], [([user_pk], 1)])
     tx = tx.sign([b.me_private])
     b.write_transaction(tx, durability='hard')
 
@@ -27,7 +27,7 @@ def test_get_stale(b, user_pk):
 def test_reassign_transactions(b, user_pk):
     from bigchaindb.models import Transaction
     # test with single node
-    tx = Transaction.create([b.me], [user_pk])
+    tx = Transaction.create([b.me], [([user_pk], 1)])
     tx = tx.sign([b.me_private])
     b.write_transaction(tx, durability='hard')
 
@@ -36,7 +36,7 @@ def test_reassign_transactions(b, user_pk):
     stm.reassign_transactions(tx.to_dict())
 
     # test with federation
-    tx = Transaction.create([b.me], [user_pk])
+    tx = Transaction.create([b.me], [([user_pk], 1)])
     tx = tx.sign([b.me_private])
     b.write_transaction(tx, durability='hard')
 
@@ -51,7 +51,7 @@ def test_reassign_transactions(b, user_pk):
     assert reassigned_tx['assignee'] != tx['assignee']
 
     # test with node not in federation
-    tx = Transaction.create([b.me], [user_pk])
+    tx = Transaction.create([b.me], [([user_pk], 1)])
     tx = tx.sign([b.me_private]).to_dict()
     tx.update({'assignee': 'lol'})
     tx.update({'assignment_timestamp': time.time()})
@@ -85,7 +85,7 @@ def test_full_pipeline(monkeypatch, user_pk):
     monkeypatch.setattr('time.time', lambda: 1)
 
     for i in range(100):
-        tx = Transaction.create([b.me], [user_pk])
+        tx = Transaction.create([b.me], [([user_pk], 1)])
         tx = tx.sign([b.me_private])
         original_txc.append(tx.to_dict())
 
diff --git a/tests/pipelines/test_vote.py b/tests/pipelines/test_vote.py
index 0810db18..f61bf253 100644
--- a/tests/pipelines/test_vote.py
+++ b/tests/pipelines/test_vote.py
@@ -8,7 +8,7 @@ from multipipes import Pipe, Pipeline
 
 def dummy_tx(b):
     from bigchaindb.models import Transaction
-    tx = Transaction.create([b.me], [b.me])
+    tx = Transaction.create([b.me], [([b.me], 1)])
     tx = tx.sign([b.me_private])
     return tx
 
@@ -130,7 +130,7 @@ def test_vote_validate_transaction(b):
     assert validation == (True, 123, 1)
 
     # NOTE: Submit unsigned transaction to `validate_tx` yields `False`.
-    tx = Transaction.create([b.me], [b.me])
+    tx = Transaction.create([b.me], [([b.me], 1)])
     validation = vote_obj.validate_tx(tx, 456, 10)
     assert validation == (False, 456, 10)
 
@@ -224,7 +224,7 @@ def test_valid_block_voting_with_create_transaction(b, monkeypatch):
 
     # create a `CREATE` transaction
     test_user_priv, test_user_pub = crypto.generate_key_pair()
-    tx = Transaction.create([b.me], [test_user_pub])
+    tx = Transaction.create([b.me], [([test_user_pub], 1)])
     tx = tx.sign([b.me_private])
 
     monkeypatch.setattr('time.time', lambda: 1)
@@ -265,7 +265,7 @@ def test_valid_block_voting_with_transfer_transactions(monkeypatch, b):
 
     # create a `CREATE` transaction
     test_user_priv, test_user_pub = crypto.generate_key_pair()
-    tx = Transaction.create([b.me], [test_user_pub])
+    tx = Transaction.create([b.me], [([test_user_pub], 1)])
     tx = tx.sign([b.me_private])
 
     monkeypatch.setattr('time.time', lambda: 1)
@@ -274,7 +274,8 @@ def test_valid_block_voting_with_transfer_transactions(monkeypatch, b):
 
     # create a `TRANSFER` transaction
     test_user2_priv, test_user2_pub = crypto.generate_key_pair()
-    tx2 = Transaction.transfer(tx.to_inputs(), [test_user2_pub], tx.asset)
+    tx2 = Transaction.transfer(tx.to_inputs(), [([test_user2_pub], 1)],
+                               tx.asset)
     tx2 = tx2.sign([test_user_priv])
 
     monkeypatch.setattr('time.time', lambda: 2)
@@ -338,7 +339,7 @@ def test_unsigned_tx_in_block_voting(monkeypatch, b, user_pk):
     vote_pipeline.setup(indata=inpipe, outdata=outpipe)
 
     # NOTE: `tx` is invalid, because it wasn't signed.
-    tx = Transaction.create([b.me], [b.me])
+    tx = Transaction.create([b.me], [([b.me], 1)])
     block = b.create_block([tx])
 
     inpipe.put(block.to_dict())
@@ -375,7 +376,7 @@ def test_invalid_id_tx_in_block_voting(monkeypatch, b, user_pk):
     vote_pipeline.setup(indata=inpipe, outdata=outpipe)
 
     # NOTE: `tx` is invalid, because its id is not corresponding to its content
-    tx = Transaction.create([b.me], [b.me])
+    tx = Transaction.create([b.me], [([b.me], 1)])
     tx = tx.sign([b.me_private])
     block = b.create_block([tx]).to_dict()
     block['block']['transactions'][0]['id'] = 'an invalid tx id'
@@ -414,7 +415,7 @@ def test_invalid_content_in_tx_in_block_voting(monkeypatch, b, user_pk):
     vote_pipeline.setup(indata=inpipe, outdata=outpipe)
 
     # NOTE: `tx` is invalid, because its content is not corresponding to its id
-    tx = Transaction.create([b.me], [b.me])
+    tx = Transaction.create([b.me], [([b.me], 1)])
     tx = tx.sign([b.me_private])
     block = b.create_block([tx]).to_dict()
     block['block']['transactions'][0]['id'] = 'an invalid tx id'
diff --git a/tests/test_models.py b/tests/test_models.py
index afde33fb..f462e3fe 100644
--- a/tests/test_models.py
+++ b/tests/test_models.py
@@ -5,7 +5,7 @@ class TestTransactionModel(object):
     def test_validating_an_invalid_transaction(self, b):
         from bigchaindb.models import Transaction
 
-        tx = Transaction.create([b.me], [b.me])
+        tx = Transaction.create([b.me], [([b.me], 1)])
         tx.operation = 'something invalid'
 
         with raises(TypeError):
@@ -41,7 +41,7 @@ class TestBlockModel(object):
         from bigchaindb.common.util import gen_timestamp, serialize
         from bigchaindb.models import Block, Transaction
 
-        transactions = [Transaction.create([b.me], [b.me])]
+        transactions = [Transaction.create([b.me], [([b.me], 1)])]
         timestamp = gen_timestamp()
         voters = ['Qaaa', 'Qbbb']
         expected_block = {
@@ -73,7 +73,7 @@ class TestBlockModel(object):
         from bigchaindb.common.util import gen_timestamp, serialize
         from bigchaindb.models import Block, Transaction
 
-        transactions = [Transaction.create([b.me], [b.me])]
+        transactions = [Transaction.create([b.me], [([b.me], 1)])]
         timestamp = gen_timestamp()
         voters = ['Qaaa', 'Qbbb']
         expected = Block(transactions, b.me, timestamp, voters)
@@ -113,7 +113,7 @@ class TestBlockModel(object):
         from bigchaindb.common.util import gen_timestamp, serialize
         from bigchaindb.models import Block, Transaction
 
-        transactions = [Transaction.create([b.me], [b.me])]
+        transactions = [Transaction.create([b.me], [([b.me], 1)])]
         timestamp = gen_timestamp()
         voters = ['Qaaa', 'Qbbb']
 
@@ -136,7 +136,7 @@ class TestBlockModel(object):
     def test_compare_blocks(self, b):
         from bigchaindb.models import Block, Transaction
 
-        transactions = [Transaction.create([b.me], [b.me])]
+        transactions = [Transaction.create([b.me], [([b.me], 1)])]
 
         assert Block() != 'invalid comparison'
         assert Block(transactions) == Block(transactions)
@@ -146,7 +146,7 @@ class TestBlockModel(object):
         from bigchaindb.common.util import gen_timestamp, serialize
         from bigchaindb.models import Block, Transaction
 
-        transactions = [Transaction.create([b.me], [b.me])]
+        transactions = [Transaction.create([b.me], [([b.me], 1)])]
         timestamp = gen_timestamp()
         voters = ['Qaaa', 'Qbbb']
         expected_block = {
@@ -168,7 +168,7 @@ class TestBlockModel(object):
         from unittest.mock import Mock
         from bigchaindb.models import Transaction
 
-        tx = Transaction.create([b.me], [b.me])
+        tx = Transaction.create([b.me], [([b.me], 1)])
         block = b.create_block([tx])
 
         has_previous_vote = Mock()
diff --git a/tests/web/conftest.py b/tests/web/conftest.py
index f6d9f9c6..988b0912 100644
--- a/tests/web/conftest.py
+++ b/tests/web/conftest.py
@@ -25,7 +25,7 @@ def app(request, node_config):
     restore_config(request, node_config)
 
     from bigchaindb.web import server
-    app = server.create_app({'debug': True})
+    app = server.create_app(debug=True)
     return app
 
 
diff --git a/tests/web/test_info.py b/tests/web/test_info.py
new file mode 100644
index 00000000..759600c5
--- /dev/null
+++ b/tests/web/test_info.py
@@ -0,0 +1,5 @@
+def test_api_endpoint_shows_basic_info(client):
+    from bigchaindb import version
+    res = client.get('/')
+    assert res.json['software'] == 'BigchainDB'
+    assert res.json['version'] == version.__version__
diff --git a/tests/web/test_basic_views.py b/tests/web/test_transactions.py
similarity index 86%
rename from tests/web/test_basic_views.py
rename to tests/web/test_transactions.py
index 9fa75758..2bc27d0c 100644
--- a/tests/web/test_basic_views.py
+++ b/tests/web/test_transactions.py
@@ -25,18 +25,11 @@ def test_get_transaction_returns_404_if_not_found(client):
     assert res.status_code == 404
 
 
-def test_api_endpoint_shows_basic_info(client):
-    from bigchaindb import version
-    res = client.get('/')
-    assert res.json['software'] == 'BigchainDB'
-    assert res.json['version'] == version.__version__
-
-
 def test_post_create_transaction_endpoint(b, client):
     from bigchaindb.models import Transaction
     user_priv, user_pub = crypto.generate_key_pair()
 
-    tx = Transaction.create([user_pub], [user_pub])
+    tx = Transaction.create([user_pub], [([user_pub], 1)])
     tx = tx.sign([user_priv])
 
     res = client.post(TX_ENDPOINT, data=json.dumps(tx.to_dict()))
@@ -48,7 +41,7 @@ def test_post_create_transaction_with_invalid_id(b, client):
     from bigchaindb.models import Transaction
     user_priv, user_pub = crypto.generate_key_pair()
 
-    tx = Transaction.create([user_pub], [user_pub])
+    tx = Transaction.create([user_pub], [([user_pub], 1)])
     tx = tx.sign([user_priv]).to_dict()
     tx['id'] = 'invalid id'
 
@@ -60,7 +53,7 @@ def test_post_create_transaction_with_invalid_signature(b, client):
     from bigchaindb.models import Transaction
     user_priv, user_pub = crypto.generate_key_pair()
 
-    tx = Transaction.create([user_pub], [user_pub])
+    tx = Transaction.create([user_pub], [([user_pub], 1)])
     tx = tx.sign([user_priv]).to_dict()
     tx['transaction']['fulfillments'][0]['fulfillment'] = 'invalid signature'
 
@@ -77,7 +70,8 @@ def test_post_transfer_transaction_endpoint(b, client, user_pk, user_sk):
 
     input_valid = b.get_owned_ids(user_pk).pop()
     create_tx = b.get_transaction(input_valid.txid)
-    transfer_tx = Transaction.transfer(create_tx.to_inputs(), [user_pub], create_tx.asset)
+    transfer_tx = Transaction.transfer(create_tx.to_inputs(),
+                                       [([user_pub], 1)], create_tx.asset)
     transfer_tx = transfer_tx.sign([user_sk])
 
     res = client.post(TX_ENDPOINT, data=json.dumps(transfer_tx.to_dict()))
@@ -94,7 +88,8 @@ def test_post_invalid_transfer_transaction_returns_400(b, client, user_pk, user_
 
     input_valid = b.get_owned_ids(user_pk).pop()
     create_tx = b.get_transaction(input_valid.txid)
-    transfer_tx = Transaction.transfer(create_tx.to_inputs(), [user_pub], create_tx.asset)
+    transfer_tx = Transaction.transfer(create_tx.to_inputs(),
+                                       [([user_pub], 1)], create_tx.asset)
 
     res = client.post(TX_ENDPOINT, data=json.dumps(transfer_tx.to_dict()))
     assert res.status_code == 400