Add test for failing assertion

Should contain function name that caused the failure (see pull request #1631).

testing/python/fixture.py

@@ -490,6 +490,20 @@ class TestRequestBasic:
         print(ss.stack)
         assert teardownlist == [1]
 
+    def test_mark_as_fixture_with_prefix_and_decorator_fails(self, testdir):
+        testdir.makeconftest("""
+            import pytest
+
+            @pytest.fixture
+            def pytest_funcarg__marked_with_prefix_and_decorator():
+                pass
+        """)
+        result = testdir.runpytest_subprocess()
+        assert result.ret != 0
+        result.stdout.fnmatch_lines([
+            "*AssertionError:*pytest_funcarg__marked_with_prefix_and_decorator*"
+        ])
+
     def test_request_addfinalizer_failing_setup(self, testdir):
         testdir.makepyfile("""
             import pytest