### Question:
Http2ConnectionHandler extends ByteToMessageDecoder implements Http2LifecycleManager, ChannelOutboundHandler { public void onHttpServerUpgrade(final Http2Settings settings) throws Http2Exception { if (!connection().isServer()) { throw Http2Exception.connectionError( Http2Error.PROTOCOL_ERROR, "Server-side HTTP upgrade requested for a client"); } if (!prefaceSent()) { throw Http2Exception.connectionError( Http2Error.INTERNAL_ERROR, "HTTP upgrade must occur after preface was sent"); } if (decoder.prefaceReceived()) { throw Http2Exception.connectionError( Http2Error.PROTOCOL_ERROR, "HTTP upgrade must occur before HTTP/2 preface is received"); } encoder.remoteSettings(settings); connection().remote().createStream(Http2CodecUtil.HTTP_UPGRADE_STREAM_ID, true); } 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 onHttpServerUpgradeWithoutHandlerAdded() throws Exception { handler = new Http2ConnectionHandlerBuilder() .frameListener(new Http2FrameAdapter()) .server(true) .build(); try { handler.onHttpServerUpgrade(new Http2Settings()); fail(); } catch (final Http2Exception e) { assertEquals(Http2Error.INTERNAL_ERROR, e.error()); } }