public OpenConfigLogicalChannelsHandler addChannel(OpenConfigChannelHandler channel) {
        modelObject.addToChannel(channel.getModelObject());
        return this;
    }
@Test
    public void testAddChannel() {
        // test Handler
        OpenConfigLogicalChannelsHandler logicalChannels = new OpenConfigLogicalChannelsHandler(parent);

        // call addChannel
        OpenConfigChannelHandler channel = new OpenConfigChannelHandler(1, logicalChannels);

        // expected ModelObject
        DefaultLogicalChannels modelObject = new DefaultLogicalChannels();
        DefaultChannel chan = new DefaultChannel();
        chan.index(1);
        modelObject.addToChannel(chan);

        assertEquals("[NG]addChannel:ModelObject(Channel added) is not an expected one.\n",
                     modelObject, logicalChannels.getModelObject());
    }