2 files changed, 42 insertions, 2 deletions
diff --git a/tests/hazmat/backends/test_openssl.py b/tests/hazmat/backends/test_openssl.py
index 962959b9..9c8fea2a 100644
--- a/tests/hazmat/backends/test_openssl.py
+++ b/tests/hazmat/backends/test_openssl.py
@@ -24,7 +24,8 @@ from cryptography.hazmat.primitives.ciphers.modes import CBC
 
 
 class DummyMode(object):
-    pass
+    def validate_for_algorithm(self, algorithm):
+        pass
 
 
 @utils.register_interface(interfaces.CipherAlgorithm)
diff --git a/tests/hazmat/primitives/test_block.py b/tests/hazmat/primitives/test_block.py
index 02de3861..7c4331e0 100644
--- a/tests/hazmat/primitives/test_block.py
+++ b/tests/hazmat/primitives/test_block.py
@@ -36,6 +36,11 @@ class DummyCipher(object):
     pass
 
 
+class DummyMode(object):
+    def validate_for_algorithm(self, algorithm):
+        pass
+
+
 class TestCipher(object):
     def test_creates_encryptor(self, backend):
         cipher = Cipher(
@@ -103,7 +108,7 @@ class TestCipherContext(object):
 
     def test_nonexistent_cipher(self, backend):
         cipher = Cipher(
-            DummyCipher(), object(), backend
+            DummyCipher(), DummyMode(), backend
         )
         with pytest.raises(UnsupportedAlgorithm):
             cipher.encryptor()
@@ -145,3 +150,37 @@ class TestAEADCipherContext(object):
         ),
         skip_message="Does not support AES GCM",
     )
+
+
+class TestModeValidation(object):
+    def test_cbc(self, backend):
+        with pytest.raises(ValueError):
+            Cipher(
+                algorithms.AES(b"\x00" * 16),
+                modes.CBC(b"abc"),
+                backend,
+            )
+
+    def test_ofb(self, backend):
+        with pytest.raises(ValueError):
+            Cipher(
+                algorithms.AES(b"\x00" * 16),
+                modes.OFB(b"abc"),
+                backend,
+            )
+
+    def test_cfb(self, backend):
+        with pytest.raises(ValueError):
+            Cipher(
+                algorithms.AES(b"\x00" * 16),
+                modes.CFB(b"abc"),
+                backend,
+            )
+
+    def test_ctr(self, backend):
+        with pytest.raises(ValueError):
+            Cipher(
+                algorithms.AES(b"\x00" * 16),
+                modes.CTR(b"abc"),
+                backend,
+            )