Objective

Understand testing techniques for Spring applications, including unit testing of controllers and services, and integration testing of REST APIs. Learn to secure Spring Boot applications using Spring Security, implementing basic authentication, database-backed user authentication, and JWT-based authorization.

Lecture Topics

1. Testing in Spring

• Overview:

  • Testing ensures the reliability and correctness of Spring applications.
  • Types: Unit testing (isolating components) and integration testing (testing components together).

• Tools and Frameworks:

  • JUnit 5: Standard testing framework for Java.
  • Mockito: For mocking dependencies in unit tests.
  • Spring Test: Provides utilities for testing Spring applications (e.g., @SpringBootTest, MockMvc).
  • TestRestTemplate: For integration testing of REST APIs.

• Dependencies (for Spring Boot):

  <dependency>
      <groupId>org.springframework.boot</groupId>
      <artifactId>spring-boot-starter-test</artifactId>
      <scope>test</scope>
  </dependency>
  
  

  • Includes JUnit 5, Mockito, AssertJ, and Spring Test.

2. Unit Testing of Spring MVC Controllers

• Purpose: Test controller logic in isolation, mocking dependencies (e.g., services).

• Key Tools:

  • MockMvc: Simulates HTTP requests and verifies responses without starting a server.
  • @WebMvcTest: Loads only the web layer (controllers, filters, etc.) for testing.

• Example:

  import com.example.controller.EmployeeController;
  import com.example.model.Employee;
  import com.example.service.EmployeeService;
  import org.junit.jupiter.api.Test;
  import org.springframework.beans.factory.annotation.Autowired;
  import org.springframework.boot.test.autoconfigure.web.servlet.WebMvcTest;
  import org.springframework.boot.test.mock.mockito.MockBean;
  import org.springframework.test.web.servlet.MockMvc;
  import static org.mockito.Mockito.when;
  import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
  import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.jsonPath;
  import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.status;
  
  @WebMvcTest(EmployeeController.class)
  public class EmployeeControllerTest {
      @Autowired
      private MockMvc mockMvc;
  
      @MockBean
      private EmployeeService employeeService;
  
      @Test
      public void testGetEmployeeById() throws Exception {
          Employee employee = new Employee(1, "John Doe", "Developer");
          when(employeeService.getById(1)).thenReturn(employee);
  
          mockMvc.perform(get("/api/employees/1"))
                 .andExpect(status().isOk())
                 .andExpect(jsonPath("$.id").value(1))
                 .andExpect(jsonPath("$.name").value("John Doe"));
      }
  }
  
  

3. Unit Testing of Spring Service Layer

• Purpose: Test business logic in services, mocking repositories or other dependencies.

• Key Tools: Mockito for mocking dependencies, JUnit for assertions.

• Example:

  import com.example.model.Employee;
  import com.example.repository.EmployeeRepository;
  import com.example.service.EmployeeService;
  import org.junit.jupiter.api.Test;
  import org.springframework.beans.factory.annotation.Autowired;
  import org.springframework.boot.test.context.SpringBootTest;
  import org.springframework.boot.test.mock.mockito.MockBean;
  import java.util.Optional;
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.mockito.Mockito.when;
  
  @SpringBootTest
  public class EmployeeServiceTest {
      @Autowired
      private EmployeeService employeeService;
  
      @MockBean
      private EmployeeRepository employeeRepository;
  
      @Test
      public void testGetById() {
          Employee employee = new Employee(1, "John Doe", "Developer");
          when(employeeRepository.findById(1)).thenReturn(Optional.of(employee));
  
          Employee result = employeeService.getById(1);
          assertEquals("John Doe", result.getName());
      }
  }
  
  

4. Integration Testing of Spring MVC Applications: REST API

• Purpose: Test the entire application stack (controllers, services, repositories, database) to ensure components work together.

• Key Tools:

  • @SpringBootTest: Loads the full application context.
  • TestRestTemplate: Sends HTTP requests to a running server.

• Example:

  import com.example.model.Employee;
  import org.junit.jupiter.api.Test;
  import org.springframework.beans.factory.annotation.Autowired;
  import org.springframework.boot.test.context.SpringBootTest;
  import org.springframework.boot.test.web.client.TestRestTemplate;
  import org.springframework.http.ResponseEntity;
  import static org.junit.jupiter.api.Assertions.assertEquals;
  
  @SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
  public class EmployeeApiIntegrationTest {
      @Autowired
      private TestRestTemplate restTemplate;
  
      @Test
      public void testGetAllEmployees() {
          ResponseEntity<Employee[]> response = restTemplate.getForEntity("/api/employees", Employee[].class);
          assertEquals(200, response.getStatusCodeValue());
      }
  }