Fix overriding of fixtures with parametrization.

_pytest/python.py

@@ -1830,7 +1830,10 @@ def pytest_generate_tests(self, metafunc):
                 if fixturedef.params is not None:
                     func_params = getattr(getattr(metafunc.function, 'parametrize', None), 'args', [[None]])
                     # skip directly parametrized arguments
-                    if argname not in func_params:
+                    argnames = func_params[0]
+                    if not isinstance(argnames, (tuple, list)):
+                        argnames = [x.strip() for x in argnames.split(",") if x.strip()]
+                    if argname not in func_params and argname not in argnames:
                         metafunc.parametrize(argname, fixturedef.params,
                                              indirect=True, scope=fixturedef.scope,
                                              ids=fixturedef.ids)

testing/python/fixture.py

@@ -1614,6 +1614,26 @@ def test_issue(foo, foobar):
         reprec = testdir.inline_run()
         reprec.assertoutcome(passed=9)
 
+    @pytest.mark.parametrize('param_args', ["'fixt, val'", "'fixt,val'", "['fixt', 'val']", "('fixt', 'val')"])
+    def test_override_parametrized_fixture_issue_979(self, testdir, param_args):
+        """Make sure a parametrized argument can override a parametrized fixture.
+
+        This was a regression introduced in the fix for #736.
+        """
+        testdir.makepyfile("""
+            import pytest
+
+            @pytest.fixture(params=[1, 2])
+            def fixt(request):
+                return request.param
+
+            @pytest.mark.parametrize(%s, [(3, 'x'), (4, 'x')])
+            def test_foo(fixt, val):
+                pass
+        """ % param_args)
+        reprec = testdir.inline_run()
+        reprec.assertoutcome(passed=2)
+
     def test_scope_session(self, testdir):
         testdir.makepyfile("""
             import pytest