private long testPut(MovieServlet movieServlet) throws IOException, ServletException { HttpServletRequest request = mock(HttpServletRequest.class); HttpServletResponse response = mock(HttpServletResponse.class); BufferedReader reader = new BufferedReader(new StringReader("{" + TEST_MOVIE_JSON + "}")); when(request.getReader()).thenReturn(reader); StringWriter stringWriter = new StringWriter(); PrintWriter writer = new PrintWriter(stringWriter); when(response.getWriter()).thenReturn(writer); movieServlet.doPut(request, response); String responseString = stringWriter.toString(); Pattern pattern = Pattern.compile("\\{\"id\":(\\d+)\\}"); Matcher matcher = pattern.matcher(responseString); assertTrue(matcher.matches()); return Long.parseLong(matcher.group(1)); }