如何测试带有依赖的Spring Boot控制器？（JUnit）

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Why This Happens #

The @WebMvcTest annotation is a slice test designed specifically for testing Spring MVC controllers. It only initializes components related to MVC (like controllers, request handlers, and view resolvers) — it doesn't load your full Spring application context. That's why Spring can't find your AnnoyingServiceWhichIsADependency bean: it's not being registered in the test context.

Solutions #

1. Mock the Dependency (Recommended for Unit Tests)

Since controller tests should focus on the controller's logic (not the service's implementation), use @MockBean to create a mock instance of your service. Spring will automatically inject this mock into your controller:

@RunWith(SpringRunner.class)
@WebMvcTest(ClassToBeTested.class)
public class ClassToBeTestedTests {
    @Autowired
    private MockMvc mockMvc;

    // Create a mock of your dependency
    @MockBean
    private AnnoyingServiceWhichIsADependency annoyingDependency;

    @Test
    public void simpleTestMethodToGetClassWorking(){
        Assert.assertTrue(true);
    }

    // Example: Test controller logic with mocked service behavior
    @Test
    public void testControllerEndpoint() throws Exception {
        // Define what the mock service should return
        when(annoyingDependency.someMethod()).thenReturn("test response");

        // Perform a request and validate the result
        mockMvc.perform(get("/your-controller-endpoint"))
               .andExpect(status().isOk())
               .andExpect(content().string("test response"));
    }
}

2. Import the Real Service (Use Sparingly)

If you absolutely need the real service implementation in your test, use @Import to add it to the test context:

@RunWith(SpringRunner.class)
@WebMvcTest(ClassToBeTested.class)
@Import(AnnoyingServiceWhichIsADependency.class)
public class ClassToBeTestedTests {
    @Autowired
    private MockMvc mockMvc;

    @Test
    public void simpleTestMethodToGetClassWorking(){
        Assert.assertTrue(true);
    }
}

⚠️ Note: If your service has its own dependencies, you'll need to import those too — this can quickly make your test complex and defeat the purpose of a slice test.

3. Use Full Context Integration Test

If you need to test the complete end-to-end flow (controller + service + dependencies), switch to @SpringBootTest with @AutoConfigureMockMvc:

@RunWith(SpringRunner.class)
@SpringBootTest
@AutoConfigureMockMvc
public class ClassToBeTestedTests {
    @Autowired
    private MockMvc mockMvc;

    @Test
    public void simpleTestMethodToGetClassWorking(){
        Assert.assertTrue(true);
    }
}

This loads your full application context, so all beans are initialized. Keep in mind this is slower than a slice test, so reserve it for integration scenarios.

Final Recommendation #

Stick with Option 1 for most controller unit tests. Mocking dependencies keeps your tests fast, focused, and isolated from changes in other parts of your application.

内容的提问来源于stack exchange，提问作者Slippy