Initial work on a prioritized multibackend for which implements CipherBackend
diff --git a/tests/conftest.py b/tests/conftest.py
index ecad1b2..00c44ca 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -4,13 +4,16 @@
 from cryptography.hazmat.backends.interfaces import (
     HMACBackend, CipherBackend, HashBackend, PBKDF2HMACBackend
 )
+from cryptography.hazmat.backends.multibackend import PrioritizedMultiBackend
 
 from .utils import check_for_iface, check_backend_support, select_backends
 
 
 def pytest_generate_tests(metafunc):
     names = metafunc.config.getoption("--backend")
-    selected_backends = select_backends(names, _ALL_BACKENDS)
+    selected_backends = select_backends(
+        names, _ALL_BACKENDS + [PrioritizedMultiBackend(_ALL_BACKENDS)]
+    )
 
     if "backend" in metafunc.fixturenames:
         metafunc.parametrize("backend", selected_backends)