Junit And Mockito Testing In Spring Boot

Junit And Mockito Overview

JUnit is a popular testing framework for Java programming language. It provides annotations to identify test methods, assertions for verifying expected results, and other utilities for testing Java code. JUnit helps in automating the process of testing code, ensuring its correctness and reliability.

Mockito, on the other hand, is a mocking framework that allows you to create mock objects in your tests. Mock objects simulate the behavior of real objects in controlled ways, enabling you to isolate the code under test and verify interactions with dependencies.

Add Dependency

To use Mockito and JUnit in a Maven project, you need to include the following dependencies in your project.

Mockito

For Maven:

<dependency>
    <groupId>org.mockito</groupId>
    <artifactId>mockito-core</artifactId>
    <version>3.11.2</version> <!-- Replace with the latest version -->
    <scope>test</scope>
</dependency>

For Gradle:

testImplementation 'org.mockito:mockito-core:3.11.2' // Replace with the latest version

Junit

For Maven:

<dependency>
    <groupId>org.junit.jupiter</groupId>
    <artifactId>junit-jupiter-engine</artifactId>
    <version>5.8.2</version> <!-- Replace with the latest version -->
    <scope>test</scope>
</dependency>

For Gradle:

testImplementation 'org.junit.jupiter:junit-jupiter-engine:5.8.2' // Replace with the latest version

Implementation

Here’s an example of writing test cases using JUnit 5 and Mockito in a Spring Boot application:

Let’s assume we have a simple service class LearnSpringBootOnlineUserService that interacts with a repository to perform user-related operations:

import org.springframework.beans.factory.annotation.Autowired;
import org.springframework.stereotype.Service;

@Service
public class LearnSpringBootOnlineUserService {

    @Autowired
    private LearnSpringBootOnlineUserRepository learnSpringBootOnlineUserRepository;

    public User getUserById(Long userId) {
        return learnSpringBootOnlineUserRepository.findById(userId).orElse(null);
    }

    public User saveUser(User user) {
        return learnSpringBootOnlineUserRepository.save(user);
    }

    public void deleteUser(Long userId) {
        learnSpringBootOnlineUserRepository.deleteById(userId);
    }
}

And we have a LearnSpringBootOnlineUserRepository interface:

import org.springframework.data.jpa.repository.JpaRepository;

public interface LearnSpringBootOnlineUserRepository extends JpaRepository<User, Long> {
}

Now let’s write test cases for the LearnSpringBootOnlineUserService class using JUnit 5 and Mockito:

import static org.junit.jupiter.api.Assertions.*;
import static org.mockito.Mockito.*;

import org.junit.jupiter.api.Test;
import org.junit.jupiter.api.extension.ExtendWith;
import org.mockito.InjectMocks;
import org.mockito.Mock;
import org.mockito.junit.jupiter.MockitoExtension;

@ExtendWith(MockitoExtension.class)
public class LearnSpringBootOnlineUserServiceTest {

    @Mock
    private LearnSpringBootOnlineUserRepository learnSpringBootOnlineUserRepository;

    @InjectMocks
    private LearnSpringBootOnlineUserService learnSpringBootOnlineUserService;

    @Test
    public void testGetUserById() {
        // Mocking behavior of userRepository
        User mockUser = new User(1L, "John Doe", "john@example.com");
        when(learnSpringBootOnlineUserRepository.findById(1L)).thenReturn(java.util.Optional.of(mockUser));

        // Calling the method under test
        User result = learnSpringBootOnlineUserService.getUserById(1L);

        // Verifying the result
        assertNotNull(result);
        assertEquals("John Doe", result.getName());
        assertEquals("john@example.com", result.getEmail());
    }

    @Test
    public void testSaveUser() {
        // Mocking behavior of LearnSpringBootOnlineUserRepository
        User userToSave = new User(null, "Alice", "alice@example.com");
        User savedUser = new User(1L, "Alice", "alice@example.com");
when(learnSpringBootOnlineUserRepository.save(userToSave)).thenReturn(savedUser);

        // Calling the method under test
        User result = learnSpringBootOnlineUserService.saveUser(userToSave);

        // Verifying the result
        assertNotNull(result);
        assertEquals(1L, result.getId());
        assertEquals("Alice", result.getName());
        assertEquals("alice@example.com", result.getEmail());
    }

    @Test
    public void testDeleteUser() {
        // Calling the method under test
        learnSpringBootOnlineUserService.deleteUser(1L);

        // Verifying that the deleteById method of LearnSpringBootOnlineUserRepository was called with the correct argument
        verify(learnSpringBootOnlineUserRepository).deleteById(1L);
    }
}

In these test cases, we use Mockito to mock the LearnSpringBootOnlineUserRepository dependency of the LearnSpringBootOnlineUserService. We then inject this mocked repository into the LearnSpringBootOnlineUserService using the @InjectMocks annotation. Finally, we write test methods to test the functionality of the LearnSpringBootOnlineUserService methods, such as getUserById(), saveUser(), and deleteUser().

Conclusion

In conclusion, the test cases presented utilize JUnit 5 and Mockito to verify the functionality of a LearnSpringBootOnlineUserService in a Spring Boot application.

Mockito is employed to mock the LearnSpringBootOnlineUserRepository, allowing for controlled behavior during testing.
JUnit 5 provides the framework for defining test methods and assertions, ensuring the correctness of the tested functionality.
Each test method follows a typical Arrange-Act-Assert pattern:
- Arranging the necessary preconditions and mock behavior,
- Acting by invoking the methods under test, and
- Asserting the expected results.
Additionally, Mockito’s verify() method is utilized to confirm interactions with the mock repository.

These test cases offer a comprehensive approach to testing the LearnSpringBootOnlineUserService, ensuring its correctness and reliability in handling user-related operations within a Spring Boot environment.

LEARN SPRING BOOT ONLINE

Junit And Mockito Testing In Spring Boot

Table of Contents

Junit And Mockito Overview

Add Dependency

Implementation

Conclusion

Useful Links

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