When using a test double for backends, always use one which really implements the interface

1 files changed, 5 insertions, 11 deletions

diff --git a/tests/hazmat/primitives/test_hashes.py b/tests/hazmat/primitives/test_hashes.py
index 0fdd7550..053a1a46 100644
--- a/tests/hazmat/primitives/test_hashes.py
+++ b/tests/hazmat/primitives/test_hashes.py
@@ -20,13 +20,12 @@ import pytest
 import six
 
 from cryptography import utils
-from cryptography.exceptions import (
-    AlreadyFinalized, _Reasons
-)
+from cryptography.exceptions import AlreadyFinalized, _Reasons
 from cryptography.hazmat.backends.interfaces import HashBackend
 from cryptography.hazmat.primitives import hashes, interfaces
 
 from .utils import generate_base_hash_test
+from ..backends.test_multibackend import DummyHashBackend
 from ...utils import raises_unsupported_algorithm
 
 
@@ -45,16 +44,11 @@ class TestHashContext(object):
             m.update(six.u("\u00FC"))
 
     def test_copy_backend_object(self):
-        @utils.register_interface(HashBackend)
-        class PretendBackend(object):
-            pass
-
-        pretend_backend = PretendBackend()
+        backend = DummyHashBackend([hashes.SHA1])
         copied_ctx = pretend.stub()
         pretend_ctx = pretend.stub(copy=lambda: copied_ctx)
-        h = hashes.Hash(hashes.SHA1(), backend=pretend_backend,
-                        ctx=pretend_ctx)
-        assert h._backend is pretend_backend
+        h = hashes.Hash(hashes.SHA1(), backend=backend, ctx=pretend_ctx)
+        assert h._backend is backend
         assert h.copy()._backend is h._backend
 
     def test_hash_algorithm_instance(self, backend):