code: @Test public void processValidModel() throws IOException {
    final HttpServletRequest request=Mockito.mock(HttpServletRequest.class);
    final HttpServletResponse response=Mockito.mock(HttpServletResponse.class,Mockito.RETURNS_DEEP_STUBS);
    Mockito.when(request.getRequestURI()).thenReturn("/app/g1.css");
    Mockito.doAnswer(new Answer<Void>(){
      public Void answer(    final InvocationOnMock invocation) throws Throwable {
        LOG.debug("Header: {}",Arrays.toString(invocation.getArguments()));
        final Object[] arguments=invocation.getArguments();
        if (HttpHeader.ETAG.toString().equals(arguments[0])) {
          final String etagHeaderValue=(String)arguments[1];
          Assert.assertTrue(etagHeaderValue.matches("\".*?\""));
        }
        return null;
      }
    }
  ).when(response).setHeader(Mockito.anyString(),Mockito.anyString());
    Context.set(Context.webContext(request,response,Mockito.mock(FilterConfig.class)));
    managerFactory.create().process();
  }
  