Spring Boot Backend Development Course, Learning the Concept of Test Code

Hello! In this course, we will take a deep dive into one of the important elements of Spring Boot backend development:
test code. While developing real applications, we need to write many tests to validate whether the functionalities
are working correctly. Test code is a key means to ensure the quality of the software and enhance maintainability and reliability.

1. Importance of Test Code

Test code has the following importance in the software development process.

  • Bug Detection: Test code helps in early detection of bugs that may arise as side effects of code changes.
  • Function Validation: It allows us to check how well the developed functionalities meet the requirements.
  • Refactoring Safety: It ensures that existing functionalities still work when refactoring the code.
  • Documentation: Test code also serves to document the usage and intention of the written code.

2. Types of Tests in Spring Boot

There are several main types of tests in Spring Boot. Each test has different purposes and usage methods.

  • Unit Test: Verifies the functionality of individual methods or classes. JUnit and Mockito are primarily used.
  • Integration Test: Verifies that multiple components work together. The @SpringBootTest annotation is used.
  • End-to-End Test: Tests the entire flow of the application. Tools like Selenium are utilized.

2.1 Unit Test

Unit tests test the smallest units of software. They generally target methods or classes, and since tests
should be independent, external dependencies are removed using mocking. In Spring Boot,
JUnit and Mockito are most commonly used. Here is a simple example of a unit test. 

import org.junit.jupiter.api.Test;
import org.mockito.Mockito;

import static org.junit.jupiter.api.Assertions.assertEquals;

public class CalculatorTest {
    @Test
    public void testAdd() {
        Calculator calculator = new Calculator();
        assertEquals(5, calculator.add(2, 3));
    }
}

2.2 Integration Test

Integration tests test interactions between multiple components. In Spring Boot, the @SpringBootTest
annotation is used to load the application context and test interactions with the database.
Here is an example of an integration test. 

import org.junit.jupiter.api.Test;
import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.test.context.ActiveProfiles;

import static org.junit.jupiter.api.Assertions.assertNotNull;

@SpringBootTest
@ActiveProfiles("test")
public class UserServiceTest {
    @Autowired
    private UserService userService;

    @Test
    public void testUserServiceNotNull() {
        assertNotNull(userService);
    }
}

2.3 End-to-End Test

End-to-end tests simulate actual user behavior to test the overall performance of the application.
Tools like Selenium can be used to automate user flows in the browser. Here is
a simple example of an end-to-end test. 

import org.junit.jupiter.api.Test;
import org.springframework.boot.test.context.SpringBootTest;
import org.springframework.boot.test.web.server.LocalServerPort;
import org.springframework.test.web.servlet.MockMvc;
import org.springframework.test.web.servlet.setup.MockMvcBuilders;
import org.springframework.web.context.WebApplicationContext;

@SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT)
public class AppTest {
    @LocalServerPort
    private int port;

    private MockMvc mockMvc;

    @Autowired
    private WebApplicationContext context;

    @BeforeEach
    public void setup() {
        this.mockMvc = MockMvcBuilders.webAppContextSetup(this.context).build();
    }

    @Test
    public void testHomePage() throws Exception {
        mockMvc.perform(get("/"))
                .andExpect(status().isOk())
                .andExpect(content().string(containsString("Hello!")));
    }
}

3. Best Practices for Writing Tests

To effectively write test code, several best practices should be followed.

  • Tests should be independent: Each test should not affect other tests.
  • Use clear names: The names of test methods should clearly indicate what is being verified by the test.
  • Single Responsibility Principle: Each test should verify only one functionality, which enhances the readability and maintainability of the code.
  • Test Data Management: The data used in tests should be consistent and reliable, and should be initialized every time the test runs.

4. Testing Support in Spring Boot

Spring Boot provides various features to make it easy to write tests.
Let’s look at some important features.

  • Test Profiles: The @TestPropertySource annotation can be used to configure database connections and settings for testing.
  • MockMvc: MockMvc can be used to send HTTP requests and verify responses without a server, testing the web layer of controllers.
  • Spring Test: The Spring @Transactional annotation can be used to reset the state of the database after each test is completed.

5. Test Automation and CI/CD

After writing test code, it is important to automate it for continuous validation.
By using CI/CD (Continuous Integration and Continuous Deployment) tools, tests can be automatically executed with every code change.

CI/CD tools like Jenkins, GitLab CI, and GitHub Actions can be used to set up test automation.
This ensures that tests are always passing before merging code into the main branch.

6. Conclusion

In this article, we learned about test code, which is a key aspect of Spring Boot backend development.
Test code is a very important element for enhancing software quality and reliability.
In the process of writing and utilizing test code in actual projects, it may take a lot of time at first, but
in the long run, it helps reduce maintenance costs and increases reliability.
I hope you continue to write and improve test code.

References