MultivaluedMap<String, String> headers = new MultivaluedHashMap<>();
when(cr.getStatusInfo()).thenReturn(mock(Response.StatusType.class));
when(cr.getStringHeaders()).thenReturn(headers);
DefaultHttpHeaders httpHeaders = new DefaultHttpHeaders();
MultiMap vertxHeaders = new HeadersAdaptor(httpHeaders);
vertxHeaders.add(HttpHeaders.CONTENT_LENGTH, "12");
when(response.headers()).thenReturn(vertxHeaders);
OutputStream outputStream = writer.writeResponseStatusAndHeaders(12, cr);
outputStream.write("callback".getBytes());