func retrieveListenerType(l *listener.Listener) string {
	nHTTP := 0
	nTCP := 0
	for _, filterChain := range getFilterChains(l) {
		for _, filter := range filterChain.GetFilters() {
			if filter.Name == HTTPListener {
				nHTTP++
			} else if filter.Name == TCPListener {
				if !strings.Contains(string(filter.GetTypedConfig().GetValue()), util.BlackHoleCluster) {
					nTCP++
				}
			}

    {
        Build target = new Build();
        target.setFilters( Arrays.asList( "first", "second", "third" ) );
        Build source = new Build();
        source.setFilters( Arrays.asList( "first", "second", "third" ) );

        modelMerger.mergeBuild( target, source, true, null );

        assertThat( target.getFilters(), contains( "first", "second", "third" ) );
    }

    @Test