### Question:
TagNotificationFilter implements NotificationFilter { @Override public FilterPolicy filterEvent(Event event, DocumentReference user, Collection<NotificationFilterPreference> filterPreferences, NotificationFormat format) { return FilterPolicy.NO_EFFECT; }  @Override FilterPolicy filterEvent(Event event, DocumentReference user,
            Collection<NotificationFilterPreference> filterPreferences, NotificationFormat format); @Override boolean matchesPreference(NotificationPreference preference); @Override ExpressionNode filterExpression(DocumentReference user,
            Collection<NotificationFilterPreference> filterPreferences, NotificationPreference preference); @Override ExpressionNode filterExpression(DocumentReference user,
            Collection<NotificationFilterPreference> filterPreferences, NotificationFilterType type,
            NotificationFormat format); @Override String getName(); static final String NAME; }### Answer:
@Test public void filterEvent() { assertEquals(NotificationFilter.FilterPolicy.NO_EFFECT, tagNotificationFilter.filterEvent(null, null, null, null)); }