Snippet

Isolated Controller Validation Testing with @WebMvcTest

@WebMvcTest loads only the web layer without bootstrapping full service and repository context. In combination with MockMvc and @MockBean, it enables focused testing of HTTP status codes, payload serialization, and Jakarta Bean Validation constraints.

snippet.java

java

@WebMvcTest(UserController.class)
class UserControllerTest {
 
    @Autowired
    private MockMvc mockMvc;
 
    @MockBean
    private UserService userService;
 
    @Test
    void whenInvalidEmail_thenReturnsUnprocessableEntity() throws Exception {
        String invalidPayload = "{\"email\": \"not-an-email\"}";
 
        mockMvc.perform(post("/api/users")
                .contentType(MediaType.APPLICATION_JSON)
                .content(invalidPayload))
            .andExpect(status().isUnprocessableEntity())
            .andExpect(jsonPath("$.errors[0].field").value("email"));
    }
}

spring

Breakdown

@WebMvcTest(UserController.class)

Instantiates only the specified controller and underlying Spring MVC infrastructure components.

@MockBean private UserService userService;

Injects a Mockito mock into the application context to isolate the web layer from business logic.

mockMvc.perform(post("/api/users")...)

Simulates an incoming HTTP POST request with a JSON payload against the endpoint.

.andExpect(status().isUnprocessableEntity())

Asserts that the validation failure triggers an HTTP 422 response status.

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Isolated Controller Validation Testing with @WebMvcTest

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