@WebMvcTest Purpose

Direct Answer

@WebMvcTest is a Spring Boot MVC test slice. It limits scanning to controllers and other supported MVC-related types, applies MVC-focused auto-configuration, and auto-configures MockMvc without opening a server port. Ordinary service and repository beans are not discovered, but filters, controller advice, converters, security configuration types, imports, and test bean overrides can all be part of the context.

Code Example

@WebMvcTest(OrderController.class)
class OrderControllerTest {

    @Autowired
    private MockMvc mockMvc;

    @MockBean
    private OrderService orderService; // Service not loaded, must mock it

    @Test
    void shouldReturnOrderById() throws Exception {
        var order = new Order(1L, "Laptop", 999.99);
        when(orderService.findById(1L)).thenReturn(Optional.of(order));

        mockMvc.perform(get("/api/orders/1")) // Simulate GET request
               .andExpect(status().isOk())
               .andExpect(jsonPath("$.id").value(1))
               .andExpect(jsonPath("$.item").value("Laptop"));
    }
}

Common Mistakes & Pitfalls

• Leaving a required collaborator absent: Supply it as @MockitoBean, older @MockBean, or imported real configuration according to the test boundary.
• Assuming fixed performance: The slice usually loads less than a broad context, but imports, filters, security, and custom configuration still affect startup.
• Assuming every mock must be stubbed: Stub only calls whose default Mockito result does not express the scenario. The failure from an unstubbed call depends on the controller behavior.