### Question:
RackResponsePropagator { private void propagateHeaders(RackResponse rackResponse, HttpServletResponse response) { for (Map.Entry<String, String> header : rackResponse.getHeaders().entrySet()) { if (shouldPropagateHeaderToClient(header)) { for (String val : header.getValue().split("\n")) { response.addHeader(header.getKey(), val); } } } try { response.flushBuffer(); } catch (IOException e) { Throwables.propagate(e); } }  void propagate(RackResponse rackResponse, HttpServletResponse response);  }### Answer:
@Test public void propagateHeaders() { rackResponse.header("Content-Type", "text/plain"); subject.propagate(rackResponse.build(), response); verify(response).addHeader("Content-Type", "text/plain"); }