### Question:
Http2ConnectionHandler extends ByteToMessageDecoder implements Http2LifecycleManager, ChannelOutboundHandler { @Override public void handlerAdded(final ChannelHandlerContext ctx) throws Exception { encoder.lifecycleManager(this); decoder.lifecycleManager(this); encoder.flowController().channelHandlerContext(ctx); decoder.flowController().channelHandlerContext(ctx); byteDecoder = new PrefaceDecoder(ctx); } protected  Http2ConnectionHandler(
      final Http2ConnectionDecoder decoder,
      final Http2ConnectionEncoder encoder,
      final Http2Settings initialSettings); protected  Http2ConnectionHandler(
      final Http2ConnectionDecoder decoder,
      final Http2ConnectionEncoder encoder,
      final Http2Settings initialSettings,
      final boolean decoupleCloseAndGoAway); long gracefulShutdownTimeoutMillis(); void gracefulShutdownTimeoutMillis(final long gracefulShutdownTimeoutMillis); Http2Connection connection(); Http2ConnectionDecoder decoder(); Http2ConnectionEncoder encoder(); void onHttpClientUpgrade(); void onHttpServerUpgrade(final Http2Settings settings); @Override void flush(final ChannelHandlerContext ctx); @Override void handlerAdded(final ChannelHandlerContext ctx); @Override void channelActive(final ChannelHandlerContext ctx); @Override void channelInactive(final ChannelHandlerContext ctx); @Override void channelWritabilityChanged(final ChannelHandlerContext ctx); @Override void bind(
      final ChannelHandlerContext ctx,
      final SocketAddress localAddress,
      final ChannelPromise promise); @Override void connect(
      final ChannelHandlerContext ctx,
      final SocketAddress remoteAddress,
      final SocketAddress localAddress,
      final ChannelPromise promise); @Override void disconnect(final ChannelHandlerContext ctx, final ChannelPromise promise); @Override void close(
      final ChannelHandlerContext ctx,
      @SuppressWarnings("checkstyle:finalparameters") ChannelPromise promise); @Override void deregister(final ChannelHandlerContext ctx, final ChannelPromise promise); @Override void read(final ChannelHandlerContext ctx); @Override void write(final ChannelHandlerContext ctx, final Object msg, final ChannelPromise promise); @Override void channelReadComplete(final ChannelHandlerContext ctx); @Override void exceptionCaught(final ChannelHandlerContext ctx, final Throwable cause); @Override void closeStreamLocal(final Http2Stream stream, final ChannelFuture future); @Override void closeStreamRemote(final Http2Stream stream, final ChannelFuture future); @Override void closeStream(final Http2Stream stream, final ChannelFuture future); @Override void onError(
      final ChannelHandlerContext ctx, final boolean outbound, final Throwable cause); @Override ChannelFuture resetStream(
      final ChannelHandlerContext ctx,
      final int streamId,
      final long errorCode,
      final ChannelPromise promise); @Override ChannelFuture goAway(
      final ChannelHandlerContext ctx,
      final int lastStreamId,
      final long errorCode,
      final ByteBuf debugData,
      ChannelPromise promise);  }### Answer:
@Test public void verifyChannelHandlerCanBeReusedInPipeline() throws Exception { when(connection.isServer()).thenReturn(true); handler = newHandler(); final ByteBuf preface = connectionPrefaceBuf(); handler.channelRead(ctx, preface); verify(decoder, never()) .decodeFrame( any(ChannelHandlerContext.class), any(ByteBuf.class), ArgumentMatchers.<List<Object>>any()); handler.handlerRemoved(ctx); handler.handlerAdded(ctx); final ByteBuf prefacePlusSome = addSettingsHeader(Unpooled.buffer().writeBytes(connectionPrefaceBuf())); handler.channelRead(ctx, prefacePlusSome); verify(decoder, atLeastOnce()) .decodeFrame(eq(ctx), any(ByteBuf.class), ArgumentMatchers.<List<Object>>any()); }
@Test public void prefaceUserEventProcessed() throws Exception { final CountDownLatch latch = new CountDownLatch(1); handler = new Http2ConnectionHandler(decoder, encoder, new Http2Settings()) { @Override public void userEventTriggered(final ChannelHandlerContext ctx, final Object evt) throws Exception { if (evt == Http2ConnectionPrefaceAndSettingsFrameWrittenEvent.INSTANCE) { latch.countDown(); } } }; handler.handlerAdded(ctx); assertTrue(latch.await(5, SECONDS)); }