def METHOD_NAME(self):
    logdir = self.get_temp_dir()
    with test_util.FileWriter(os.path.join(logdir, "a")) as writer:
        writer.add_test_summary("tag_a")
    with test_util.FileWriter(os.path.join(logdir, "b")) as writer:
        writer.add_test_summary("tag_b")
    with test_util.FileWriter(os.path.join(logdir, "b", "x")) as writer:
        writer.add_test_summary("tag_b_x")
    writer_c = test_util.FileWriter(os.path.join(logdir, "c"))
    writer_c.add_test_summary("tag_c")
    writer_c.flush()
    loader = self._create_logdir_loader(logdir)
    loader.synchronize_runs()
    self.assertEqual(
        self._extract_run_to_tags(loader.get_run_events()),
        {
            "a": ["tag_a"],
            "b": ["tag_b"],
            "b/x": ["tag_b_x"],
            "c": ["tag_c"],
        },
    )
    # A second load should indicate no new data.
    self.assertEqual(
        self._extract_run_to_tags(loader.get_run_events()),
        {"a": [], "b": [], "b/x": [], "c": []},
    )
    # Write some new data to both new and pre-existing event files.
    with test_util.FileWriter(
        os.path.join(logdir, "a"), filename_suffix=".other"
    ) as writer:
        writer.add_test_summary("tag_a_2")
        writer.add_test_summary("tag_a_3")
        writer.add_test_summary("tag_a_4")
    with test_util.FileWriter(
        os.path.join(logdir, "b", "x"), filename_suffix=".other"
    ) as writer:
        writer.add_test_summary("tag_b_x_2")
    with writer_c as writer:
        writer.add_test_summary("tag_c_2")
    # New data should appear on the next load.
    self.assertEqual(
        self._extract_run_to_tags(loader.get_run_events()),
        {
            "a": ["tag_a_2", "tag_a_3", "tag_a_4"],
            "b": [],
            "b/x": ["tag_b_x_2"],
            "c": ["tag_c_2"],
        },
    )