### Question:
DefaultChannelPipeline implements ChannelPipeline { @Override public String toString() { StringBuilder buf = new StringBuilder(); buf.append(getClass().getSimpleName()); buf.append('{'); DefaultChannelHandlerContext ctx = head; if (ctx != null) { for (;;) { buf.append('('); buf.append(ctx.getName()); buf.append(" = "); buf.append(ctx.getHandler().getClass().getName()); buf.append(')'); ctx = ctx.next; if (ctx == null) { break; } buf.append(", "); } } buf.append('}'); return buf.toString(); }  Channel getChannel(); ChannelSink getSink(); void attach(Channel channel, ChannelSink sink); boolean isAttached(); synchronized void addFirst(String name, ChannelHandler handler); synchronized void addLast(String name, ChannelHandler handler); synchronized void addBefore(String baseName, String name, ChannelHandler handler); synchronized void addAfter(String baseName, String name, ChannelHandler handler); synchronized void remove(ChannelHandler handler); synchronized ChannelHandler remove(String name); @SuppressWarnings("unchecked") synchronized T remove(Class<T> handlerType); synchronized ChannelHandler removeFirst(); synchronized ChannelHandler removeLast(); synchronized void replace(ChannelHandler oldHandler, String newName, ChannelHandler newHandler); synchronized ChannelHandler replace(String oldName, String newName, ChannelHandler newHandler); @SuppressWarnings("unchecked") synchronized T replace(
            Class<T> oldHandlerType, String newName, ChannelHandler newHandler); synchronized ChannelHandler getFirst(); synchronized ChannelHandler getLast(); synchronized ChannelHandler get(String name); synchronized T get(Class<T> handlerType); synchronized ChannelHandlerContext getContext(String name); synchronized ChannelHandlerContext getContext(ChannelHandler handler); synchronized ChannelHandlerContext getContext(
            Class<? extends ChannelHandler> handlerType); List<String> getNames(); Map<String, ChannelHandler> toMap(); @Override String toString(); void sendUpstream(ChannelEvent e); void sendDownstream(ChannelEvent e); ChannelFuture execute(Runnable task);  }### Answer:
@Test public void testToString() { DefaultChannelPipeline pipeline = new DefaultChannelPipeline(); assertNotNull(pipeline.toString()); }