How to unit test a Spring MVC controller using @PathVariable?

I have a simple annotated controller similar to this one:

@Controller
public class MyController {
  @RequestMapping("/{id}.html")
  public String doSomething(@PathVariable String id, Model model) {
    // do something
    return "view";
  }
}

and I want to test it with an unit test like this:

public class MyControllerTest {
  @Test
  public void test() {
    MockHttpServletRequest request = new MockHttpServletRequest();
    request.setRequestURI("/test.html");
    new AnnotationMethodHandlerAdapter()
      .handle(request, new MockHttpServletResponse(), new MyController());
    // assert something
  }
}

The problem is that AnnotationMethodHandlerAdapter.handler() method throws an exception:

java.lang.IllegalStateException: Could not find @PathVariable [id] in @RequestMapping
at org.springframework.web.servlet.mvc.annotation.AnnotationMethodHandlerAdapter$ServletHandlerMethodInvoker.resolvePathVariable(AnnotationMethodHandlerAdapter.java:642)
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.resolvePathVariable(HandlerMethodInvoker.java:514)
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.resolveHandlerArguments(HandlerMethodInvoker.java:262)
at org.springframework.web.bind.annotation.support.HandlerMethodInvoker.invokeHandlerMethod(HandlerMethodInvoker.java:146)

I'd call what you're after an integration test based on the terminology in the Spring reference manual. How about doing something like:

import static org.springframework.test.web.ModelAndViewAssert.*;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration({/* include live config here
    e.g. "file:web/WEB-INF/application-context.xml",
    "file:web/WEB-INF/dispatcher-servlet.xml" */})
public class MyControllerIntegrationTest {

    @Inject
    private ApplicationContext applicationContext;

    private MockHttpServletRequest request;
    private MockHttpServletResponse response;
    private HandlerAdapter handlerAdapter;
    private MyController controller;

    @Before
    public void setUp() {
       request = new MockHttpServletRequest();
       response = new MockHttpServletResponse();
       handlerAdapter = applicationContext.getBean(HandlerAdapter.class);
       // I could get the controller from the context here
       controller = new MyController();
    }

    @Test
    public void testDoSomething() throws Exception {
       request.setRequestURI("/test.html");
       final ModelAndView mav = handlerAdapter.handle(request, response, 
           controller);
       assertViewName(mav, "view");
       // assert something
    }
}

For more information I've written a blog entry about integration testing Spring MVC annotations.

As of Spring 3.2, there is a proper way to test this, in an elegant and easy way. You will be able to do things like this:

@RunWith(SpringJUnit4ClassRunner.class)
@WebAppConfiguration
@ContextConfiguration("servlet-context.xml")
public class SampleTests {

  @Autowired
  private WebApplicationContext wac;

  private MockMvc mockMvc;

  @Before
  public void setup() {
    this.mockMvc = webAppContextSetup(this.wac).build();
  }

  @Test
  public void getFoo() throws Exception {
    this.mockMvc.perform(get("/foo").accept("application/json"))
        .andExpect(status().isOk())
        .andExpect(content().mimeType("application/json"))
        .andExpect(jsonPath("$.name").value("Lee"));
  }
}

For further information, take a look at http://blog.springsource.org/2012/11/12/spring-framework-3-2-rc1-spring-mvc-test-framework/

A promising framework for testing Spring MVC https://github.com/SpringSource/spring-test-mvc

The exception message refers to a "feed" variable, which isn't present in your sample code, it's likely being caused by something you haven't shown us.

Also, your test is testing Spring and your own code. Is this really what you want to do?

It's better to assume that Spring works (which it does), and just test your own class, i.e. call MyController.doSomething() directly. That's one benefit of the annotation approach - you don't need to use mock requests and responses, you just use domain POJOs.

I've found that you can manually insert a PathVariable mapping into the request object. This is distinctly non-ideal but appears to work. In your example, something like:

@Test
public void test() {
    MockHttpServletRequest request = new MockHttpServletRequest();
    request.setRequestURI("/test.html");
    HashMap<String, String> pathvars = new HashMap<String, String>();
    pathvars.put("id", "test");
    request.setAttribute(HandlerMapping.URI_TEMPLATE_VARIABLES_ATTRIBUTE, pathvars);
    new AnnotationMethodHandlerAdapter().handle(request, new MockHttpServletResponse(), new MyController());
   // assert something
}

I'd definitely be interested in finding a better option.