diff --git a/bigchaindb/tendermint/utils.py b/bigchaindb/tendermint/utils.py
index 28c4bb3c..3deb8b2c 100644
--- a/bigchaindb/tendermint/utils.py
+++ b/bigchaindb/tendermint/utils.py
@@ -4,13 +4,13 @@ import sha3
 
 
 def encode_transaction(value):
-    """Encode a transaction to Base64."""
+    """Encode a transaction (dict) to Base64."""
 
     return base64.b64encode(json.dumps(value).encode('utf8')).decode('utf8')
 
 
 def decode_transaction(raw):
-    """Decode a transaction from Base64 to a dict."""
+    """Decode a transaction from bytes to a dict."""
 
     return json.loads(raw.decode('utf8'))
 
diff --git a/tests/tendermint/test_lib.py b/tests/tendermint/test_lib.py
index 714f0b2d..6cf28719 100644
--- a/tests/tendermint/test_lib.py
+++ b/tests/tendermint/test_lib.py
@@ -3,6 +3,7 @@ import os
 import pytest
 
 from bigchaindb import backend
+from unittest.mock import patch
 
 
 pytestmark = pytest.mark.tendermint
@@ -46,3 +47,39 @@ def test_get_latest_block(b):
 
     block = b.get_latest_block()
     assert block['height'] == 9
+
+
+def test_validation_error(b):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.crypto import generate_key_pair
+
+    alice = generate_key_pair()
+    tx = Transaction.create([alice.public_key],
+                            [([alice.public_key], 1)],
+                            asset=None)\
+                    .sign([alice.private_key]).to_dict()
+
+    tx['metadata'] = ''
+    assert not b.validate_transaction(tx)
+
+
+@patch('requests.post')
+def test_write_and_post_transaction(mock_post, b):
+    from bigchaindb.models import Transaction
+    from bigchaindb.common.crypto import generate_key_pair
+    from bigchaindb.tendermint.utils import encode_transaction
+
+    alice = generate_key_pair()
+    tx = Transaction.create([alice.public_key],
+                            [([alice.public_key], 1)],
+                            asset=None)\
+                    .sign([alice.private_key]).to_dict()
+
+    tx = b.validate_transaction(tx)
+    b.write_transaction(tx)
+
+    assert mock_post.called
+    args, kwargs = mock_post.call_args
+    assert 'broadcast_tx_async' == kwargs['json']['method']
+    encoded_tx = [encode_transaction(tx.to_dict())]
+    assert encoded_tx == kwargs['json']['params']
diff --git a/tests/tendermint/test_utils.py b/tests/tendermint/test_utils.py
index e69de29b..ce91c173 100644
--- a/tests/tendermint/test_utils.py
+++ b/tests/tendermint/test_utils.py
@@ -0,0 +1,27 @@
+import base64
+import json
+
+
+def test_encode_decode_transaction(b):
+    from bigchaindb.tendermint.utils import (encode_transaction,
+                                             decode_transaction)
+
+    asset = {
+        'value': 'key'
+    }
+
+    encode_tx = encode_transaction(asset)
+    new_encode_tx = base64.b64encode(json.dumps(asset).
+                                     encode('utf8')).decode('utf8')
+
+    assert encode_tx == new_encode_tx
+
+    de64 = base64.b64decode(encode_tx)
+    assert asset == decode_transaction(de64)
+
+
+def test_calculate_hash_no_key(b):
+    from bigchaindb.tendermint.utils import calculate_hash
+
+    # pass an empty list
+    assert calculate_hash([]) == ''