import py failure_demo = py.path.local(__file__).dirpath("failure_demo.py") pytest_plugins = ("pytester",) def test_failure_demo_fails_properly(testdir): target = testdir.tmpdir.join(failure_demo.basename) failure_demo.copy(target) failure_demo.copy(testdir.tmpdir.join(failure_demo.basename)) result = testdir.runpytest(target, syspathinsert=True) result.stdout.fnmatch_lines(["*42 failed*"]) assert result.ret != 0