### Question:
Http2ConnectionHandler extends ByteToMessageDecoder implements Http2LifecycleManager,
                                                                            ChannelOutboundHandler { @Override public ChannelFuture resetStream(final ChannelHandlerContext ctx, int streamId, long errorCode, ChannelPromise promise) { final Http2Stream stream = connection().stream(streamId); if (stream == null) { return resetUnknownStream(ctx, streamId, errorCode, promise.unvoid()); } return resetStream(ctx, stream, errorCode, promise); } 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 writeRstOnNonExistantStreamShouldSucceed() throws Exception { handler = newHandler(); when(frameWriter.writeRstStream(eq(ctx), eq(NON_EXISTANT_STREAM_ID), eq(STREAM_CLOSED.code()), eq(promise))).thenReturn(future); handler.resetStream(ctx, NON_EXISTANT_STREAM_ID, STREAM_CLOSED.code(), promise); verify(frameWriter).writeRstStream(eq(ctx), eq(NON_EXISTANT_STREAM_ID), eq(STREAM_CLOSED.code()), eq(promise)); }
@Test public void writeRstOnClosedStreamShouldSucceed() throws Exception { handler = newHandler(); when(stream.id()).thenReturn(STREAM_ID); when(frameWriter.writeRstStream(eq(ctx), eq(STREAM_ID), anyLong(), any(ChannelPromise.class))).thenReturn(future); when(stream.state()).thenReturn(CLOSED); when(stream.isHeadersSent()).thenReturn(true); handler.resetStream(ctx, STREAM_ID, STREAM_CLOSED.code(), promise); verify(frameWriter).writeRstStream(eq(ctx), eq(STREAM_ID), anyLong(), any(ChannelPromise.class)); }