Test code is essential in software development. Especially when developing large-scale applications, it is common to modify code or add new features. Each time this happens, it is difficult to be sure where the failure may occur, so it is important to write reliable test code. In this article, we will specifically look at how to write test code using Spring Boot.
1. What is Spring Boot?
Spring Boot is a platform for application development based on the Spring framework. It helps developers build and deploy applications easily without extensive setup. The main features of Spring Boot are as follows:
- Auto-configuration
- Standalone applications
- Minimal configuration
- Powerful module and dependency management
2. Why is test code necessary?
Test code is very important for improving the quality and maintainability of an application. With test code, we can:
- Validate that the application’s functionality is working correctly.
- Handle conditional logic and edge cases.
- Ensure that existing features remain intact after code changes.
- Manage dependencies between modules and quickly identify issues during integration testing.
3. Setting up test code in Spring Boot
The necessary library for writing test code in Spring Boot is `spring-boot-starter-test`. You set up the test environment by adding this library to `pom.xml`.
<dependency>
<groupId>org.springframework.boot</groupId>
<artifactId>spring-boot-starter-test</artifactId>
<scope>test</scope>
</dependency>Afterwards, you will create a test class using SpringJUnit4ClassRunner. Now, let’s look at several annotations that can be used in the test class.
3.1 @SpringBootTest
This annotation loads the context of the Spring Boot application, allowing for integration testing. All beans in the application are loaded, enabling testing of the entire application.
3.2 @MockBean
To efficiently test services connected to external APIs or databases, `@MockBean` can be used to mock the service. This helps strengthen the unit testing of the code.
3.3 @Autowired
This annotation allows for injection of required beans into the test class through Spring’s dependency injection. This makes it easy to validate the functionality of the class being tested.
4. Writing basic test code
Let’s first create a simple controller class.
import org.springframework.web.bind.annotation.GetMapping;
import org.springframework.web.bind.annotation.RestController;
@RestController
public class HelloController {
@GetMapping("/hello")
public String hello() {
return "Hello, World!";
}
}Now, let’s write the test code for the above controller.
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.test.web.servlet.MockMvc;
import static org.springframework.test.web.servlet.result.MockMvcResultMatchers.content;
import static org.springframework.test.web.servlet.request.MockMvcRequestBuilders.get;
@WebMvcTest(HelloController.class)
public class HelloControllerTest {
@Autowired
private MockMvc mockMvc;
@Test
public void helloTest() throws Exception {
mockMvc.perform(get("/hello"))
.andExpect(content().string("Hello, World!"));
}
}In the above code, we use the `WebMvcTest` annotation to test the `HelloController`. We simulate an HTTP GET request using `MockMvc` and validate the result.
5. Testing the service layer
To write tests for the service layer, we will use the `@SpringBootTest` annotation and now check the internal logic of the service.
import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import static org.junit.jupiter.api.Assertions.assertEquals;
@SpringBootTest
public class UserServiceTest {
@Autowired
private UserService userService;
@Test
public void testUserCreation() {
User user = new User("testUser");
userService.createUser(user);
User foundUser = userService.findUserByName("testUser");
assertEquals("testUser", foundUser.getName());
}
}In service tests, we call the actual service methods to verify the expected results. This allows us to validate the business logic through the process of creating and retrieving data.
6. Refactoring test code
There is a lot of room for improvement in test code. We can reduce duplication by extracting repetitive code into methods. Additionally, we can write common code to execute before each test using the `@BeforeEach` annotation.
import org.junit.jupiter.api.BeforeEach;
public class UserServiceTest {
@BeforeEach
public void setup() {
// Common execution code
}
@Test
public void testUserCreation() {
// Test code
}
}7. Integration testing and End-to-End testing
Integration testing validates the interaction between modules, checking whether multiple components work together. This generally includes interactions with databases and external APIs. End-to-End testing is the process of verifying that the application functions correctly from the user’s perspective.
In Spring Boot, we can efficiently test the web layer through MockMvc, and we can write integration test code that uses `@Autowired` for actual database integration testing.
8. Test coverage
Test coverage indicates how much of the code is being tested. A higher value indicates improved software quality. It is important to use tools like Jacoco to check test coverage and identify which code is excluded from testing.
9. Conclusion
Writing test code in Spring Boot is essential for increasing the reliability and maintainability of applications. We hope you utilize the various testing techniques introduced today to create reliable applications.
Testing is a crucial part of the development process and helps maintain integrity, especially in rapidly changing environments. Write proper test code to create high-quality software.