def add_test_modules_to_pythonpath(self) -> None:
        """Add our test modules directory to PYTHONPATH."""
        # Check that there isn't already a PYTHONPATH.
        assert os.getenv("PYTHONPATH") is None
        testmods = nice_file(self.working_root(), "tests/modules")
        zipfile = nice_file(self.working_root(), "tests/zipmods.zip")
        self.set_environ("PYTHONPATH", testmods + os.pathsep + zipfile)
Add our test modules directory to PYTHONPATH.
tests/coveragetest.py