@Test
  public void nullHeadersSetTest() {
    HttpRequest request = createRequestWithHeaders(HttpMethod.GET, TestingUri.SetNullHeader.toString());
    HttpUtil.setKeepAlive(request, false);
    EmbeddedChannel channel = createEmbeddedChannel();
    channel.writeInbound(request);

    HttpResponse response = channel.readOutbound();
    assertEquals("Unexpected response status", HttpResponseStatus.ACCEPTED, response.status());
    assertFalse("Channel not closed on the server", channel.isActive());
  }
Sends null input to {@link NettyResponseChannel#setHeader(String, Object)} (through
{@link MockNettyMessageProcessor}) and tests for reaction.
ambry-rest/src/test/java/com/github/ambry/rest/NettyResponseChannelTest.java