@Mock of an @Autowired dependency causes random junit test failures

Question

My spring-mvc app works. Yay! Proof:

This is my good setup:

The important bits of my Buggy-servlet.xml

<import resource="classpath:bug-core.xml" />
<mvc:annotation-driven />
<context:component-scan base-package="buggy.bug" />

The important bits of the bug-core.xml file it imports:

<bean class="org.springframework.beans.factory.annotation.AutowiredAnnotationBeanPostProcessor" />
<bean id="VersionInfoBean" class="buggy.bug.VersionInfo">
    <property name="helloWorld" value="GAHHHHH!!!" />
</bean>

The VersionInfo class:

public class VersionInfo {

    private String helloWorld;

    public String getHelloWorld() {
        return helloWorld;
    }

    public void setHelloWorld(String helloWorld) {
        this.helloWorld = helloWorld;
    }

}

And finally, the VersionInfoController class:

@RestController
@RequestMapping("/versioninfo")
public class VersionInfoController {

    @Autowired
    private VersionInfo versionInfo;

    @ResponseStatus(value = HttpStatus.OK)
    @RequestMapping(method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
    public VersionInfo getVersionInfo () {
        return versionInfo;
    }

}

It's all good!

Now the problem:

I want to unit test. I think I did good. My VersionInfoControllerTest class:

@RunWith(SpringJUnit4ClassRunner.class)
@ContextConfiguration(classes = {TestContext.class, WebAppContext.class})
@WebAppConfiguration
@TestExecutionListeners(listeners = {DependencyInjectionTestExecutionListener.class})
public class VersionInfoControllerTest {

    // TODO: apparently I cannot @Mock the VersionInfo.  Try uncommenting the below, run the test a few times and see.

    // The link is for testng, but it's nearly the same for junit, and SHOULD work!
    // https://lkrnac.net/blog/2014/01/mock-autowired-fields/

//  @Mock
//  private VersionInfo versionInfo;

    @InjectMocks
    private VersionInfoController versionInfoController;

    private MockMvc mockMvc;

    @Before
    public void setUp() {
        MockitoAnnotations.initMocks(this);
        mockMvc = MockMvcBuilders.standaloneSetup(versionInfoController).build();
    }

    @Test
    public void getVersionInfo() throws Exception {
        mockMvc.perform(get("/versioninfo")
            .accept(MediaType.APPLICATION_JSON))
            .andExpect(status().isOk());
    }
}

The WebAppContext class:

@Configuration
@EnableWebMvc
@ComponentScan(basePackages = {"buggy.bug"})
public class WebAppContext extends WebMvcConfigurerAdapter {

    @Override
    public void configureDefaultServletHandling(DefaultServletHandlerConfigurer configurer) {
        configurer.enable();
    }

}

The TestContext class:

@Configuration
public class TestContext {

    @Bean
    public VersionInfo versionInfo() {
        return Mockito.mock(VersionInfo.class);
    }
}

I run junit (either via mvn clean install or in Eclipse junit launch configuration). It's all good.

If I uncomment the two lines indicated in VersionInfoControllerTest, the test may fail or pass (more often it fails). When it fails, it fails in one of two ways:

Way one:

java.lang.AssertionError: Status expected:<200> but was:<500>
    at org.springframework.test.util.AssertionErrors.fail(AssertionErrors.java:60)
    at org.springframework.test.util.AssertionErrors.assertEquals(AssertionErrors.java:89)
    at org.springframework.test.web.servlet.result.StatusResultMatchers$10.match(StatusResultMatchers.java:655)
    at org.springframework.test.web.servlet.MockMvc$1.andExpect(MockMvc.java:171)
    at buggy.bug.VersionInfoControllerTest.getVersionInfo(VersionInfoControllerTest.java:52)
    at sun.reflect.NativeMethodAccessorImpl.invoke0(Native Method)
    at sun.reflect.NativeMethodAccessorImpl.invoke(NativeMethodAccessorImpl.java:62)
    at sun.reflect.DelegatingMethodAccessorImpl.invoke(DelegatingMethodAccessorImpl.java:43)
    at java.lang.reflect.Method.invoke(Method.java:498)
    at org.junit.runners.model.FrameworkMethod$1.runReflectiveCall(FrameworkMethod.java:47)
    at org.junit.internal.runners.model.ReflectiveCallable.run(ReflectiveCallable.java:12)
    at org.junit.runners.model.FrameworkMethod.invokeExplosively(FrameworkMethod.java:44)
    at org.junit.internal.runners.statements.InvokeMethod.evaluate(InvokeMethod.java:17)
    at org.junit.internal.runners.statements.RunBefores.evaluate(RunBefores.java:26)
    at org.springframework.test.context.junit4.statements.RunBeforeTestMethodCallbacks.evaluate(RunBeforeTestMethodCallbacks.java:75)
    at org.springframework.test.context.junit4.statements.RunAfterTestMethodCallbacks.evaluate(RunAfterTestMethodCallbacks.java:86)
    at org.springframework.test.context.junit4.statements.SpringRepeat.evaluate(SpringRepeat.java:84)
    at org.junit.runners.ParentRunner.runLeaf(ParentRunner.java:271)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:254)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.runChild(SpringJUnit4ClassRunner.java:89)
    at org.junit.runners.ParentRunner$3.run(ParentRunner.java:238)
    at org.junit.runners.ParentRunner$1.schedule(ParentRunner.java:63)
    at org.junit.runners.ParentRunner.runChildren(ParentRunner.java:236)
    at org.junit.runners.ParentRunner.access$000(ParentRunner.java:53)
    at org.junit.runners.ParentRunner$2.evaluate(ParentRunner.java:229)
    at org.springframework.test.context.junit4.statements.RunBeforeTestClassCallbacks.evaluate(RunBeforeTestClassCallbacks.java:61)
    at org.springframework.test.context.junit4.statements.RunAfterTestClassCallbacks.evaluate(RunAfterTestClassCallbacks.java:70)
    at org.junit.runners.ParentRunner.run(ParentRunner.java:309)
    at org.springframework.test.context.junit4.SpringJUnit4ClassRunner.run(SpringJUnit4ClassRunner.java:193)
    at org.eclipse.jdt.internal.junit4.runner.JUnit4TestReference.run(JUnit4TestReference.java:86)
    at org.eclipse.jdt.internal.junit.runner.TestExecution.run(TestExecution.java:38)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:459)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.runTests(RemoteTestRunner.java:675)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.run(RemoteTestRunner.java:382)
    at org.eclipse.jdt.internal.junit.runner.RemoteTestRunner.main(RemoteTestRunner.java:192)

Way two is much worse:

INFO: FrameworkServlet '': initialization completed in 1 ms
Jun 03, 2016 8:44:06 PM org.springframework.web.servlet.mvc.support.DefaultHandlerExceptionResolver handleHttpMessageNotWritable
WARNING: Failed to write HTTP message: org.springframework.http.converter.HttpMessageNotWritableException: Could not write content: Infinite recursion (StackOverflowError) (through reference chain: org.mockito.internal.stubbing.InvocationContainerImpl["invocationForStubbing"]->org.mockito.internal.invocation.InvocationMatcher["invocation"]->org.mockito.internal.invocation.InvocationImpl["mock"]->buggy.bug.VersionInfo$$EnhancerByMockitoWithCGLIB$$41545457["callbacks"]->org.mockito.internal.creation.MethodInterceptorFilter["handler"]->org.mockito.internal.handler.InvocationNotifierHandler["invocationContainer"]->org.mockito.internal.stubbing.InvocationContainerImpl["invocationForStubbing"]->org.mockito.internal.invocation.InvocationMatcher["invocation"]->org.mockito.internal.invocation.InvocationImpl["mock"]->buggy.bug.VersionInfo$$EnhancerByMockitoWithCGLIB$$41545457["callbacks"]->org.mockito.internal.creation.MethodInterceptorFilter["handler"]->org.mockito.internal.handler.InvocationNotifierHandler["invocationContainer"]->org.mockito.internal.stubbing.InvocationContainerImpl["invocationForStubbing"]->...

Since it's a StackOverflowError, repeat until out of memory.

I've put up a github project that demonstrates the problem

Any ideas? What did I do wrong? As far as I can tell I did exactly what other accepted answers on SO and blogs, forums, spring docs, all say to do to mock an @Autowired field.

Sam Brannen · Accepted Answer · 2016-06-04T12:55:04.417

There are two things going on here.

Since you're using MockMvcBuilders.standaloneSetup, you do not need to load an ApplicationContext.
Jackson cannot convert your VersionInfo object into JSON if it's a mock created by Mockito (at least not with the default mapping rules that attempt to map all properties including those introduced by Mockito).

Here's the solution:

public class VersionInfo {

    @JsonView(VersionInfo.class)
    private String helloWorld;

    public String getHelloWorld() {
        return helloWorld;
    }

    public void setHelloWorld(String helloWorld) {
        this.helloWorld = helloWorld;
    }

}

@RestController
@RequestMapping("/versioninfo")
public class VersionInfoController {

    @Autowired
    private VersionInfo versionInfo;

    @RequestMapping(method = RequestMethod.GET, produces = MediaType.APPLICATION_JSON_VALUE)
    @JsonView(VersionInfo.class)
    public VersionInfo getVersionInfo() {
        return versionInfo;
    }

}

public class VersionInfoControllerTest {

    @Mock
    private VersionInfo versionInfo;

    @InjectMocks
    private VersionInfoController versionInfoController;

    private MockMvc mockMvc;

    @Before
    public void setUp() {
        MockitoAnnotations.initMocks(this);
        mockMvc = MockMvcBuilders.standaloneSetup(versionInfoController).build();
    }

    @Test
    public void getVersionInfo() throws Exception {
        mockMvc.perform(get("/versioninfo").accept(MediaType.APPLICATION_JSON))
            .andExpect(status().isOk());
    }

}

Summary:

Use standard JUnit 4 testing support and delete everything related to the Spring TestContext Framework since you are not using an ApplicationContext.
Use @JsonView in VersionInfo to limit JSON serialization only to properties in VersionInfo.
Use @JsonView on the getVersionInfo() method in your controller to instruct Spring to use the view when invoking the Jackson JSON mapper.

Keep in mind that the use of @JsonView in this scenario is only necessary because you are mocking the return value from a controller method with Mockito.

Regards,

Sam (author of the Spring TestContext Framework)

That's it. Thank you so much. I think I finally have a good grasp of the difference between `standaloneSetup` and `webAppContextSetup`. — mikerott, Jun 05 '16 at 00:42

@Mock of an @Autowired dependency causes random junit test failures

This is my good setup:

Now the problem:

1 Answers1