Testing Controller Layer

The Testing responsibility covers unit and integration testing strategies for controllers.

Testing Strategy

Controllers are tested via integration tests using Spring’s test framework:

Use @SpringBootTest for full application context
Use MockMvc for HTTP request simulation
Mock service layer to isolate controller logic
Verify routing, status codes, response structure
Test error handling and exception mapping

Integration Test Example

@SpringBootTest
class SupplierControllerTest {
    
    @Autowired
    private MockMvc mockMvc;
    
    @MockBean
    private SupplierService supplierService;
    
    @Test
    void testCreateSupplierSuccess() throws Exception {
        // Arrange
        CreateSupplierDTO createDto = CreateSupplierDTO.builder()
            .name("ACME Corp")
            .contactName("John Doe")
            .contactEmail("john@acme.com")
            .phoneNumber("5551234567")
            .minOrderQuantity(10)
            .build();
        
        SupplierDTO savedDto = SupplierDTO.builder()
            .id("abc123")
            .name("ACME Corp")
            .contactName("John Doe")
            .build();
        
        when(supplierService.create(any(CreateSupplierDTO.class)))
            .thenReturn(savedDto);
        
        // Act & Assert
        mockMvc.perform(post("/api/suppliers")
            .contentType(MediaType.APPLICATION_JSON)
            .content(objectMapper.writeValueAsString(createDto)))
            .andExpect(status().isCreated())
            .andExpect(jsonPath("$.id").value("abc123"))
            .andExpect(jsonPath("$.name").value("ACME Corp"));
    }
    
    @Test
    void testCreateSupplierValidationFailure() throws Exception {
        // Missing required field
        CreateSupplierDTO invalidDto = CreateSupplierDTO.builder()
            .name("")  // Empty name
            .contactName("John Doe")
            .build();
        
        mockMvc.perform(post("/api/suppliers")
            .contentType(MediaType.APPLICATION_JSON)
            .content(objectMapper.writeValueAsString(invalidDto)))
            .andExpect(status().isBadRequest());
    }
    
    @Test
    void testDeleteSupplierUnauthorized() throws Exception {
        // No authorization, should fail
        mockMvc.perform(delete("/api/suppliers/abc123"))
            .andExpect(status().isForbidden());
    }
}

Testing Patterns

Test Successful Endpoint

@Test
void testGetSupplierSuccess() throws Exception {
    SupplierDTO supplier = SupplierDTO.builder()
        .id("abc123")
        .name("ACME Corp")
        .build();
    
    when(supplierService.findById("abc123"))
        .thenReturn(Optional.of(supplier));
    
    mockMvc.perform(get("/api/suppliers/abc123")
        .with(user("testuser").roles("USER")))
        .andExpect(status().isOk())
        .andExpect(jsonPath("$.id").value("abc123"));
}

Test Not Found Error

@Test
void testGetSupplierNotFound() throws Exception {
    when(supplierService.findById("nonexistent"))
        .thenReturn(Optional.empty());
    
    mockMvc.perform(get("/api/suppliers/nonexistent"))
        .andExpect(status().isNotFound());
}

Test Authorization

@Test
void testDeleteSupplierAsAdmin() throws Exception {
    mockMvc.perform(delete("/api/suppliers/abc123")
        .with(user("admin").roles("ADMIN")))
        .andExpect(status().isNoContent());
    
    verify(supplierService).delete("abc123");
}

@Test
void testDeleteSupplierAsUser() throws Exception {
    // USER role lacks permission
    mockMvc.perform(delete("/api/suppliers/abc123")
        .with(user("user").roles("USER")))
        .andExpect(status().isForbidden());
}

Test Validation

@Test
void testCreateSupplierInvalidEmail() throws Exception {
    CreateSupplierDTO invalidDto = CreateSupplierDTO.builder()
        .name("ACME Corp")
        .contactEmail("invalid-email")  // Not valid email format
        .build();
    
    mockMvc.perform(post("/api/suppliers")
        .contentType(MediaType.APPLICATION_JSON)
        .content(objectMapper.writeValueAsString(invalidDto))
        .with(user("admin").roles("ADMIN")))
        .andExpect(status().isBadRequest());
}

Test Annotations

@SpringBootTest - Loads full application context for integration tests
@MockBean - Replaces service beans with mocks
@Autowired - Injects MockMvc for simulating HTTP requests
@Test - Marks method as test case

MockMvc Methods

mockMvc.perform(request) - Execute HTTP request simulation
post(), get(), put(), delete() - HTTP method builders
.contentType(MediaType.APPLICATION_JSON) - Set request content type
.content() - Set request body
.andExpect(status().isOk()) - Assert HTTP status code
.andExpect(jsonPath()) - Assert JSON response structure
.with(user()) - Add Spring Security user context

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