public void onGlobalPropertyChange(String key, @Nullable String value) {
    GlobalPropertyChangeHandler.PropertyChange change = GlobalPropertyChangeHandler.PropertyChange.create(key, value);
    for (GlobalPropertyChangeHandler changeHandler : changeHandlers) {
      changeHandler.onChange(change);
    }
  }
@Test
  public void no_handlers() {
    SettingsChangeNotifier notifier = new SettingsChangeNotifier();

    assertThat(notifier.changeHandlers).isEmpty();

    // does not fail
    notifier.onGlobalPropertyChange("foo", "bar");
  }