ContainerResponse cr = mock(ContainerResponse.class);
MultivaluedMap<String, String> headers = new MultivaluedHashMap<>();
when(cr.getStatusInfo()).thenReturn(mock(Response.StatusType.class));
when(cr.getStringHeaders()).thenReturn(headers);
VertxResponseProcessor processor1 = mock(VertxResponseProcessor.class);
VertxResponseProcessor processor2 = mock(VertxResponseProcessor.class);
responseProcessors.add(processor1);
responseProcessors.add(processor2);
headers.add("x-test", "custom header");
OutputStream outputStream = writer.writeResponseStatusAndHeaders(15, cr);