Simplify code and add test
diff --git a/tests/hazmat/primitives/utils.py b/tests/hazmat/primitives/utils.py
index 4640c2e..6428b03 100644
--- a/tests/hazmat/primitives/utils.py
+++ b/tests/hazmat/primitives/utils.py
@@ -311,6 +311,9 @@
     with pytest.raises(ValueError):
         mode_factory(binascii.unhexlify(b"0" * 24), b"000")
 
+    with pytest.raises(ValueError):
+        mode_factory(binascii.unhexlify(b"0" * 24), b"000000", 2)
+
     cipher = Cipher(
         cipher_factory(binascii.unhexlify(b"0" * 32)),
         mode_factory(binascii.unhexlify(b"0" * 24), b"0" * 16),