Unable to mock Service class in Spring MVC Controller tests

Question

Thanks to @J Andy’s line of thought, I realised that I had been heading down the wrong path on this. In Update 1 I was trying to inject the mock service into the MockMvc but after taking a step back I realised that it’s not the MockMvc that was under test, it was the PolicyController I wanted to test.

To give a bit of background, I wanted to avoid a traditional unit test of the @Controllers in my Spring MVC application because I wanted to test things that are only provided by running the controllers within Spring itself (e.g. RESTful calls to controller actions). This can be achieved by using the Spring MVC Test framework which allows you to run your tests within Spring.

You’ll see from the code in my initial question that I was running the Spring MVC tests in a WebApplicationContext
(i.e. this.mockMvc = MockMvcBuilders.webAppContextSetup(this.wac).build();
) whereas what I should have been doing was running standalone. Running standalone allows me to directly inject the controller I want to test and, therefore, have control over how the service is injected into the controller (i.e. force a mock service to be used).

This is easier explained in code. So for the following controller:

import javax.validation.Valid;

import name.hines.steven.medical_claims_tracker.domain.Benefit;
import name.hines.steven.medical_claims_tracker.domain.Policy;
import name.hines.steven.medical_claims_tracker.services.DomainEntityService;
import name.hines.steven.medical_claims_tracker.services.PolicyService;

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Controller;
import org.springframework.validation.BindingResult;
import org.springframework.web.bind.annotation.ModelAttribute;
import org.springframework.web.bind.annotation.PathVariable;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.servlet.ModelAndView;

@Controller
@RequestMapping("/policies")
public class PolicyController extends DomainEntityController<Policy> {

    @Autowired
    private PolicyService service;

    @RequestMapping(value = "persist", method = RequestMethod.POST)
    public String createOrUpdate(@Valid @ModelAttribute("policy") Policy policy, BindingResult result) {
        if (result.hasErrors()) {
            return "createOrUpdatePolicyForm";
        }
        service.save(policy);
        return "redirect:list";
    }
}

I now have the following test class in which the service is successfully mocked out and my test database is no longer hit:

package name.hines.steven.medical_claims_tracker.controllers;

import static org.mockito.Matchers.isA;
import static org.mockito.Mockito.when;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.model;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.redirectedUrl;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.view;
import name.hines.steven.medical_claims_tracker.domain.Policy;
import name.hines.steven.medical_claims_tracker.services.PolicyService;

import org.junit.Before;
import org.junit.Test;
import org.junit.runner.RunWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.MockitoAnnotations;
import org.springframework.test.context.ContextConfiguration;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.web.servlet.MockMvc;
import org.springframework.test.web.servlet.setup.MockMvcBuilders;

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration({ "classpath:/applicationContext.xml" })
public class PolicyControllerTest {

    @Mock
    PolicyService policyService;

    @InjectMocks
    PolicyController controllerUnderTest;

    private MockMvc mockMvc;

    @Before
    public void setup() {

        // this must be called for the @Mock annotations above to be processed
        // and for the mock service to be injected into the controller under
        // test.
        MockitoAnnotations.initMocks(this);

        this.mockMvc = MockMvcBuilders.standaloneSetup(controllerUnderTest).build();

    }

    @Test
    public void createOrUpdateFailsWhenInvalidDataPostedAndSendsUserBackToForm() throws Exception {
        // POST no data to the form (i.e. an invalid POST)
        mockMvc.perform(post("/policies/persist")).andExpect(status().isOk())
        .andExpect(model().attributeHasErrors("policy"))
        .andExpect(view().name("createOrUpdatePolicy"));
    }

    @Test
    public void createOrUpdateSuccessful() throws Exception {

        when(policyService.save(isA(Policy.class))).thenReturn(new Policy());

        mockMvc.perform(
                post("/policies/persist").param("companyName", "Company Name")
                .param("name", "Name").param("effectiveDate", "2001-01-01"))
                .andExpect(status().isMovedTemporarily()).andExpect(model().hasNoErrors())
                .andExpect(redirectedUrl("list"));
    }
}

I’m still very much learning when it comes to Spring so any comments that will improve my explanation would be welcomed. This blog post was helpful to me in coming up with this solution.

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