@Test public void processesRequest() throws Exception { ContainerRequest containerRequest = mockContainerRequest(); ContainerResponse containerResponse = mockContainerResponse(); EnvironmentContext environmentContext = mock(EnvironmentContext.class); doAnswer( invocation -> { Response response = mock(Response.class); when(response.getStatus()).thenReturn(200); when(response.getEntity()).thenReturn("foo"); containerResponse.setResponse(response); return null; }) .when(requestHandler) .handleRequest(containerRequest, containerResponse); everrestProcessor.process(containerRequest, containerResponse, environmentContext); ArgumentCaptor<Response> argumentCaptor = ArgumentCaptor.forClass(Response.class); verify(containerResponse).setResponse(argumentCaptor.capture()); assertEquals(200, argumentCaptor.getValue().getStatus()); assertEquals("foo", argumentCaptor.getValue().getEntity()); }