redefined-outer-name: Add one more test case

Write the positive test of `redefined-outer-name`
(#70)

Signed-off-by: Stavros Ntentos <133706+stdedos@users.noreply.github.com>

Author: stdedos

tests/input/redefined-outer-name/caller_not_a_test_func.py

@@ -9,3 +9,7 @@ def this_is_a_fixture():
 def not_a_test_function(this_is_a_fixture):
     # invalid test case...
     assert True
+
+
+def test_function_valid(this_is_a_fixture):
+    assert True

tests/test_redefined_outer_name.py

@@ -24,7 +24,7 @@ def test_caller_yield_fixture(self, enable_plugin):
     @pytest.mark.parametrize("enable_plugin", [True, False])
     def test_caller_not_a_test_func(self, enable_plugin):
         self.run_linter(enable_plugin)
-        self.verify_messages(1)
+        self.verify_messages(1 if enable_plugin else 2)
 
     @pytest.mark.parametrize("enable_plugin", [True, False])
     def test_args_and_kwargs(self, enable_plugin):