Problem: No test for '_input_valid' memoization

Solution: Add necessary test

bigchaindb/upsert_validator/validator_election.py

@@ -30,12 +30,6 @@ class ValidatorElection(Transaction):
     CREATE = VALIDATOR_ELECTION
     ALLOWED_OPERATIONS = (VALIDATOR_ELECTION,)
 
-    # def __init__(self, operation, asset, inputs, outputs,
-    #              metadata=None, version=None, hash_id=None, tx_):
-    #     # operation `CREATE` is being passed as argument as `VALIDATOR_ELECTION` is an extension
-    #     # of `CREATE` and any validation on `CREATE` in the parent class should apply to it
-    #     super().__init__(operation, asset, inputs, outputs, metadata, version, hash_id)
-
     @classmethod
     def get_validators(cls, bigchain, height=None):
         """Return a dictionary of validators with key as `public_key` and

tests/common/test_memoize.py

@@ -65,3 +65,29 @@ def test_memoize_from_dict(b):
 
     assert from_dict.cache_info().hits == 2
     assert from_dict.cache_info().misses == 1
+
+
+def test_memoize_input_valid(b):
+    alice = generate_key_pair()
+    asset = {
+        'data': {'id': 'test_id'},
+    }
+
+    assert Transaction._input_valid.cache_info().hits == 0
+    assert Transaction._input_valid.cache_info().misses == 0
+
+    tx = Transaction.create([alice.public_key],
+                            [([alice.public_key], 1)],
+                            asset=asset,)\
+                    .sign([alice.private_key])
+
+    tx.inputs_valid()
+
+    assert Transaction._input_valid.cache_info().hits == 0
+    assert Transaction._input_valid.cache_info().misses == 1
+
+    tx.inputs_valid()
+    tx.inputs_valid()
+
+    assert Transaction._input_valid.cache_info().hits == 2
+    assert Transaction._input_valid.cache_info().misses == 1