def run_plugin(self, module_name: str) -> Coverage:
        """Run a plugin with the given module_name.

        Uses a few fixed Python files.

        Returns the Coverage object.

        """
        self.make_file("simple.py", """\
            import other, another
            a = other.f(2)
            b = other.f(3)
            c = another.g(4)
            d = another.g(5)
            """)
        # The names of these files are important: some plugins apply themselves
        # to "*other.py".
        self.make_file("other.py", """\
            def f(x):
                return x+1
            """)
        self.make_file("another.py", """\
            def g(x):
                return x-1
            """)

        cov = coverage.Coverage()
        cov.set_option("run:plugins", [module_name])
        self.start_import_stop(cov, "simple")
        cov.save()  # pytest-cov does a save after stop, so we'll do it too.
        return cov
Run a plugin with the given module_name.

        Uses a few fixed Python files.

        Returns the Coverage object.

        
tests/test_plugins.py