add mark that allows us to do skip tests on backends via decorators

3 files changed, 44 insertions, 2 deletions

diff --git a/tests/conftest.py b/tests/conftest.py
index e059b630..d8ab5819 100644
--- a/tests/conftest.py
+++ b/tests/conftest.py
@@ -4,7 +4,7 @@ from cryptography.hazmat.backends.interfaces import (
     HMACBackend, CipherBackend, HashBackend
 )
 
-from .utils import check_for_iface
+from .utils import check_for_iface, supported_by_backend_skip
 
 
 def pytest_generate_tests(metafunc):
@@ -19,3 +19,4 @@ def pytest_runtest_setup(item):
     check_for_iface("hmac", HMACBackend, item)
     check_for_iface("cipher", CipherBackend, item)
     check_for_iface("hash", HashBackend, item)
+    supported_by_backend_skip(item)
diff --git a/tests/test_utils.py b/tests/test_utils.py
index a65091ff..b347efd5 100644
--- a/tests/test_utils.py
+++ b/tests/test_utils.py
@@ -20,7 +20,8 @@ import pytest
 
 from .utils import (
     load_nist_vectors, load_vectors_from_file, load_cryptrec_vectors,
-    load_openssl_vectors, load_hash_vectors, check_for_iface
+    load_openssl_vectors, load_hash_vectors, check_for_iface,
+    supported_by_backend_skip
 )
 
 
@@ -41,6 +42,36 @@ def test_check_for_iface():
     check_for_iface("fake_name", FakeInterface, item)
 
 
+def test_supported_by_backend_skip():
+    supported = pretend.stub(
+        kwargs={"only_if": lambda backend: False, "skip_message": "Nope"}
+    )
+    item = pretend.stub(keywords={"supported": supported},
+                        funcargs={"backend": True})
+    with pytest.raises(pytest.skip.Exception) as exc_info:
+        supported_by_backend_skip(item)
+    assert exc_info.value.args[0] == "Nope"
+
+
+def test_supported_by_backend_no_skip():
+    supported = pretend.stub(
+        kwargs={"only_if": lambda backend: True, "skip_message": "Nope"}
+    )
+    item = pretend.stub(keywords={"supported": supported},
+                        funcargs={"backend": True})
+    assert supported_by_backend_skip(item) is None
+
+
+def test_supported_by_backend_skip_no_backend():
+    supported = pretend.stub(
+        kwargs={"only_if": "notalambda", "skip_message": "Nope"}
+    )
+    item = pretend.stub(keywords={"supported": supported},
+                        funcargs={})
+    with pytest.raises(TypeError):
+        supported_by_backend_skip(item)
+
+
 def test_load_nist_vectors():
     vector_data = textwrap.dedent("""
     # CAVS 11.1
diff --git a/tests/utils.py b/tests/utils.py
index 82021a5f..113488d3 100644
--- a/tests/utils.py
+++ b/tests/utils.py
@@ -24,6 +24,16 @@ def check_for_iface(name, iface, item):
             ))
 
 
+def supported_by_backend_skip(item):
+    supported = item.keywords.get("supported")
+    if supported and "backend" in item.funcargs:
+        if not supported.kwargs["only_if"](item.funcargs["backend"]):
+            pytest.skip(supported.kwargs["skip_message"])
+    elif supported:
+        raise TypeError("This mark is only available on methods that take a "
+                        "backend")
+
+
 def load_vectors_from_file(filename, loader):
     base = os.path.join(
         os.path.dirname(__file__), "hazmat", "primitives", "vectors",