Unit Testing Spring REST Controllers Via Mock MVC

2 min readOct 1, 2018

I would start off with a disclaimer that REST based controllers are better tested using integration tests or using a more suitable mocking framework like wiremock.

However, assuming that you may still want to use Mock MVC in your junit tests, we can do something like the following:

1.) Let us say we want to test a (super simplifed) controller that looks something like:


import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.http.HttpStatus;
import org.springframework.http.ResponseEntity;
import org.springframework.web.bind.annotation.RequestMapping;
import org.springframework.web.bind.annotation.RequestMethod;
import org.springframework.web.bind.annotation.RestController;

@RestController
@RequestMapping("/fizzbuzz/v1/*")
public class MyController {

    private SomeComponent bean;

    @Autowired
    public void setBean(SomeComponent bean) {
        this.bean = bean;
    }

    @RequestMapping(value="/action" , method = {RequestMethod.POST})
    public ResponseEntity<?> execute()
    {
       
        bean.setState("CREATED");
        return ResponseEntity.ok().build();
    }


}

The “SomeComponent” in the above example is managed by Spring (using the “@Component” annotation).

2.) The gradle dependencies that we will require are:

// Use JUnit test framework
testImplementation 'junit:junit:' + "${junitVersion}"
testCompile group: 'org.mockito', name: 'mockito-core', version: "${mockitoCoreVersion}"
testCompile group: 'org.springframework', name: 'spring-test', version: "${springTestVersion}"
testCompile group: 'org.springframework.boot', name: 'spring-boot-starter-test', version: "${springBootStarterTestVersion}"

3.) The test class will look something like:


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.mockito.Spy;
import org.springframework.test.context.junit4.SpringJUnit4ClassRunner;
import org.springframework.test.web.servlet.MockMvc;
import org.springframework.test.web.servlet.setup.MockMvcBuilders;

import static org.junit.Assert.assertTrue;
import static org.mockito.Mockito.atLeastOnce;
import static org.mockito.Mockito.verify;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.delete;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.post;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.put;
import static org.springframework.test.web.servlet.result.MockMvcResultHandlers.print;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;

@RunWith(SpringJUnit4ClassRunner.class)
public class LCMControllerTest {

    @InjectMocks
    private MyController controllerUnderTest;

    @Spy
    private SomeComponent bean;


    private MockMvc mockMvc;

    @Before
    public void startService() throws Exception{
        MockitoAnnotations.initMocks(this);
        mockMvc = MockMvcBuilders.standaloneSetup(controllerUnderTest).build();
    }

    @Test
    public void testExecute()throws Exception{
        mockMvc.perform(post("http://<base_url>/fizzbuzz/v1/action"))
                .andDo(print())
                .andExpect(status().isOk());
        verify(bean,atLeastOnce()).setState("CREATED");
     }
}

Obviously, this is a very simplified example and essentially illustrates the bare bones of mock mvc usage in junit tests. This however can be used to build unit tests around REST controllers.

Unit Testing Spring REST Controllers Via Mock MVC

Written by Phoenix Rising