diff --git a/tests/backend/mongodb/test_schema.py b/tests/backend/mongodb/test_schema.py
index 33ddb719..c806f433 100644
--- a/tests/backend/mongodb/test_schema.py
+++ b/tests/backend/mongodb/test_schema.py
@@ -95,7 +95,6 @@ def test_create_secondary_indexes():
 
 
 def test_drop(dummy_db):
-    import bigchaindb
     from bigchaindb import backend
     from bigchaindb.backend import schema
 
diff --git a/tests/common/test_transaction.py b/tests/common/test_transaction.py
index 038d82df..769ab002 100644
--- a/tests/common/test_transaction.py
+++ b/tests/common/test_transaction.py
@@ -154,8 +154,7 @@ def test_invalid_output_initialization(cond_uri, user_pub):
         Output(cond_uri, [user_pub], 0)
 
 
-def test_generate_output_split_half_recursive(user_pub, user2_pub,
-                                                  user3_pub):
+def test_generate_output_split_half_recursive(user_pub, user2_pub, user3_pub):
     from bigchaindb.common.transaction import Output
     from cryptoconditions import Ed25519Fulfillment, ThresholdSha256Fulfillment
 
@@ -174,8 +173,8 @@ def test_generate_output_split_half_recursive(user_pub, user2_pub,
     assert cond.fulfillment.to_dict() == expected.to_dict()
 
 
-def test_generate_outputs_split_half_single_owner(user_pub, user2_pub,
-                                                     user3_pub):
+def test_generate_outputs_split_half_single_owner(user_pub,
+                                                  user2_pub, user3_pub):
     from bigchaindb.common.transaction import Output
     from cryptoconditions import Ed25519Fulfillment, ThresholdSha256Fulfillment
 
@@ -231,8 +230,7 @@ def test_generate_output_single_owner_with_output(user_pub):
     assert cond.fulfillment.to_dict() == expected.to_dict()
 
 
-def test_generate_output_invalid_parameters(user_pub, user2_pub,
-                                                user3_pub):
+def test_generate_output_invalid_parameters(user_pub, user2_pub, user3_pub):
     from bigchaindb.common.transaction import Output
 
     with raises(ValueError):
@@ -289,7 +287,6 @@ def test_create_default_asset_on_tx_initialization(asset_definition):
 
 def test_transaction_serialization(user_input, user_output, data):
     from bigchaindb.common.transaction import Transaction
-    from .utils import validate_transaction_model
 
     tx_id = 'l0l'
 
@@ -559,7 +556,7 @@ def test_validate_multiple_inputs(user_input, user_output, user_priv,
 
     expected_first_bytes = str(expected_first).encode()
     expected_first.inputs[0].fulfillment.sign(expected_first_bytes,
-                                                    PrivateKey(user_priv))
+                                              PrivateKey(user_priv))
     expected_second_bytes = str(expected_second).encode()
     expected_second.inputs[0].fulfillment.sign(expected_second_bytes,
                                                PrivateKey(user_priv))
diff --git a/tests/conftest.py b/tests/conftest.py
index 8b7c5cb1..ea28521d 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -275,9 +275,11 @@ def inputs(user_pk, b, genesis_block):
     prev_block_id = genesis_block.id
     for block in range(4):
         transactions = [
-            Transaction.create([b.me], [([user_pk], 1)],
-                               metadata={'msg': random.random()})
-                       .sign([b.me_private])
+            Transaction.create(
+                [b.me],
+                [([user_pk], 1)],
+                metadata={'msg': random.random()},
+            ).sign([b.me_private])
             for _ in range(10)
         ]
         block = b.create_block(transactions)
@@ -297,9 +299,11 @@ def inputs_shared(user_pk, user2_pk, genesis_block):
     prev_block_id = genesis_block.id
     for block in range(4):
         transactions = [
-            Transaction.create([b.me], [user_pk, user2_pk],
-                               metadata={'msg': random.random()})
-                       .sign([b.me_private])
+            Transaction.create(
+                [b.me],
+                [user_pk, user2_pk],
+                metadata={'msg': random.random()},
+            ).sign([b.me_private])
             for _ 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 241c12a0..32487dbb 100644
--- a/tests/db/test_bigchain_api.py
+++ b/tests/db/test_bigchain_api.py
@@ -189,7 +189,7 @@ class TestBigchainApi(object):
         tx = Transaction.transfer(inputs, [([user_pk], 1)],
                                   asset_id=input_tx.id)
         tx = tx.sign([user_sk])
-        response = b.write_transaction(tx)
+        b.write_transaction(tx)
 
         tx_from_db, status = b.get_transaction(tx.id, include_status=True)