### Question:
Http2ConnectionHandler extends ByteToMessageDecoder implements Http2LifecycleManager,
                                                                            ChannelOutboundHandler { public void onHttpClientUpgrade() throws Http2Exception { if (connection().isServer()) { throw connectionError(PROTOCOL_ERROR, "Client-side HTTP upgrade requested for a server"); } if (!prefaceSent()) { throw connectionError(INTERNAL_ERROR, "HTTP upgrade must occur after preface was sent"); } if (decoder.prefaceReceived()) { throw connectionError(PROTOCOL_ERROR, "HTTP upgrade must occur before HTTP/2 preface is received"); } connection().local().createStream(HTTP_UPGRADE_STREAM_ID, true); } protected  Http2ConnectionHandler(Http2ConnectionDecoder decoder, Http2ConnectionEncoder encoder,
                                     Http2Settings initialSettings);   Http2ConnectionHandler(boolean server, Http2FrameWriter frameWriter, Http2FrameLogger frameLogger,
                    Http2Settings initialSettings); long gracefulShutdownTimeoutMillis(); void gracefulShutdownTimeoutMillis(long gracefulShutdownTimeoutMillis); Http2Connection connection(); Http2ConnectionDecoder decoder(); Http2ConnectionEncoder encoder(); void onHttpClientUpgrade(); void onHttpServerUpgrade(Http2Settings settings); @Override void flush(ChannelHandlerContext ctx); @Override void handlerAdded(ChannelHandlerContext ctx); @Override void channelActive(ChannelHandlerContext ctx); @Override void channelInactive(ChannelHandlerContext ctx); @Override void channelWritabilityChanged(ChannelHandlerContext ctx); @Override void bind(ChannelHandlerContext ctx, SocketAddress localAddress, ChannelPromise promise); @Override void connect(ChannelHandlerContext ctx, SocketAddress remoteAddress, SocketAddress localAddress,
                        ChannelPromise promise); @Override void disconnect(ChannelHandlerContext ctx, ChannelPromise promise); @Override void close(ChannelHandlerContext ctx, ChannelPromise promise); @Override void deregister(ChannelHandlerContext ctx, ChannelPromise promise); @Override void read(ChannelHandlerContext ctx); @Override void write(ChannelHandlerContext ctx, Object msg, ChannelPromise promise); @Override void channelReadComplete(ChannelHandlerContext ctx); @Override void exceptionCaught(ChannelHandlerContext ctx, Throwable cause); @Override void closeStreamLocal(Http2Stream stream, ChannelFuture future); @Override void closeStreamRemote(Http2Stream stream, ChannelFuture future); @Override void closeStream(final Http2Stream stream, ChannelFuture future); @Override void onError(ChannelHandlerContext ctx, boolean outbound, Throwable cause); @Override ChannelFuture resetStream(final ChannelHandlerContext ctx, int streamId, long errorCode,
                                     ChannelPromise promise); @Override ChannelFuture goAway(final ChannelHandlerContext ctx, final int lastStreamId, final long errorCode,
                                final ByteBuf debugData, ChannelPromise promise);  }### Answer:
@Test public void onHttpClientUpgradeWithoutHandlerAdded() throws Exception { handler = new Http2ConnectionHandlerBuilder().frameListener(new Http2FrameAdapter()).server(false).build(); try { handler.onHttpClientUpgrade(); fail(); } catch (Http2Exception e) { assertEquals(Http2Error.INTERNAL_ERROR, e.error()); } }