def make_plugin_track_render(self, filename: str) -> None:
        """Make a dynamic context plugin that tracks 'render_' functions."""
        self.make_file(filename, """\
            from coverage import CoveragePlugin

            class Plugin(CoveragePlugin):
                def dynamic_context(self, frame):
                    name = frame.f_code.co_name
                    if name.startswith("render_"):
                        return 'renderer:' + name[7:]
                    return None

            def coverage_init(reg, options):
                reg.add_dynamic_context(Plugin())
            """)
Make a dynamic context plugin that tracks 'render_' functions.
tests/test_plugins.py