Added some tests for changefeed generics

pepify import
googlify docstring

bigchaindb/backend/changefeed.py

@@ -1,6 +1,7 @@
 """Changefeed interfaces for backends."""
 
 from functools import singledispatch
+
 from multipipes import Node
 
 import bigchaindb
@@ -32,8 +33,8 @@ class ChangeFeed(Node):
                 ChangeFeed.UPDATE. Combining multiple operation is possible
                 with the bitwise ``|`` operator
                 (e.g. ``ChangeFeed.INSERT | ChangeFeed.UPDATE``)
-            prefeed (iterable): whatever set of data you want to be published
-                first.
+            prefeed (:class:`~collections.abc.Iterable`): whatever set of data
+                you want to be published first.
             connection (:class:`~bigchaindb.backend.connection.Connection`):
                 A connection to the database (can be None).
         """

tests/backend/test_generics.py

@@ -37,9 +37,31 @@ def test_schema(schema_func_name, args_qty):
     ('get_votes_by_block_id_and_voter', 2),
     ('update_transaction', 2),
     ('get_transaction_from_block', 2),
+    ('get_old_transactions', 1),
 ))
 def test_query(query_func_name, args_qty):
     from bigchaindb.backend import query
     query_func = getattr(query, query_func_name)
     with raises(NotImplementedError):
         query_func(None, *range(args_qty))
+
+
+@mark.parametrize('changefeed_func_name,args_qty', (
+    ('get_changefeed', 2),
+))
+def test_changefeed(changefeed_func_name, args_qty):
+    from bigchaindb.backend import changefeed
+    changefeed_func = getattr(changefeed, changefeed_func_name)
+    with raises(NotImplementedError):
+        changefeed_func(None, *range(args_qty))
+
+
+@mark.parametrize('changefeed_class_func_name,args_qty', (
+    ('run_forever', 0),
+    ('run_changefeed', 0),
+))
+def test_changefeed_class(changefeed_class_func_name, args_qty):
+    from bigchaindb.backend.changefeed import ChangeFeed
+    changefeed_class_func = getattr(ChangeFeed, changefeed_class_func_name)
+    with raises(NotImplementedError):
+        changefeed_class_func(None, *range(args_qty))