### Question:
DefaultChannelManager implements ChannelManager { @Override public void unregisterChannel(@NotNull String name) { this.channels.remove(name); }  @NotNull @Override Optional<NetworkChannel> getChannel(@NotNull String name); @NotNull @Override @UnmodifiableView Collection<NetworkChannel> getNetworkChannels(@NotNull String remoteAddress); @NotNull @Override Optional<NetworkChannel> getFirstChannel(); @NotNull @Override @UnmodifiableView Collection<NetworkChannel> getRegisteredChannels(); @NotNull @Override NetworkChannel createChannel(@NotNull Channel channel); @Override void registerChannel(@NotNull NetworkChannel channel); @Override void unregisterChannel(@NotNull String name);  }### Answer:
@Test @Order(5) void testUnregisterChannel() { this.channelManager.unregisterChannel("TestChannel"); Assertions.assertEquals(0, this.channelManager.getRegisteredChannels().size()); }