adding test_docker_utils to test framework

tests/test_docker_utils.py

@@ -0,0 +1,18 @@
+"""who tests the tester's tests?"""
+import pytest
+import _pytest.outcomes
+
+import prosper.common.test_helpers as p_helpers
+import prosper.common.exceptions as exceptions
+
+def test_assert_docker_regular():
+    """make sure p_helpers.assert_docker() raises expected error"""
+    p_helpers.DOCKER_OK = False
+    with pytest.raises(exceptions.DockerNotFound):
+        p_helpers.assert_docker()
+
+def test_assert_docker_xfail():
+    """make sure p_helpers.assert_docker() raises xfail in mode"""
+    p_helpers.DOCKER_OK = False
+    with pytest.raises(_pytest.outcomes.XFailed):
+        p_helpers.assert_docker(xfail=True)