Test a service that uses JDBI using junit 5 and mokito

3 min read 04-10-2024

Test a service that uses JDBI using junit 5 and mokito

Testing a JDBI Service with JUnit 5 and Mockito

When building applications that interact with databases, ensuring the robustness and correctness of data access is paramount. JDBI, a lightweight and efficient Java library, simplifies database interaction, but it's crucial to test its functionality rigorously. This article explores how to effectively test a JDBI service using JUnit 5 and Mockito, focusing on isolating dependencies and providing comprehensive coverage.

The Scenario

Let's imagine we have a service called UserService that retrieves user data from a database using JDBI. Here's a simplified representation of the UserService class:

import org.jdbi.v3.core.Jdbi;
import org.jdbi.v3.sqlobject.SqlObject;
import org.jdbi.v3.sqlobject.config.RegisterBeanMapper;
import org.jdbi.v3.sqlobject.statement.SqlQuery;

public class UserService {

    private final Jdbi jdbi;

    public UserService(Jdbi jdbi) {
        this.jdbi = jdbi;
    }

    public User findUserById(int userId) {
        UserDAO dao = jdbi.onDemand(UserDAO.class);
        return dao.findUserById(userId);
    }

    @RegisterBeanMapper(User.class)
    public interface UserDAO extends SqlObject {
        @SqlQuery("SELECT * FROM users WHERE id = :id")
        User findUserById(int id);
    }
}

Testing with JUnit 5 and Mockito

To test the UserService, we need to isolate its dependencies. JUnit 5 provides a powerful framework for testing, while Mockito allows us to mock objects and control their behavior during tests.

Here's a JUnit 5 test class:

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

import org.jdbi.v3.core.Jdbi;
import org.jdbi.v3.sqlobject.SqlObject;
import org.jdbi.v3.sqlobject.config.RegisterBeanMapper;
import org.jdbi.v3.sqlobject.statement.SqlQuery;

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

class UserServiceTest {

    @Test
    void testFindUserById() {
        Jdbi jdbiMock = Mockito.mock(Jdbi.class);
        UserDAO userDAOMock = Mockito.mock(UserDAO.class);

        // Mock the behavior of the UserDAO
        when(jdbiMock.onDemand(UserDAO.class)).thenReturn(userDAOMock);
        when(userDAOMock.findUserById(1)).thenReturn(new User(1, "John Doe"));

        UserService userService = new UserService(jdbiMock);
        User user = userService.findUserById(1);

        // Verify the expected result and interactions
        assertEquals(new User(1, "John Doe"), user);
        verify(jdbiMock, times(1)).onDemand(UserDAO.class);
        verify(userDAOMock, times(1)).findUserById(1);
    }

    @RegisterBeanMapper(User.class)
    public interface UserDAO extends SqlObject {
        @SqlQuery("SELECT * FROM users WHERE id = :id")
        User findUserById(int id);
    }
}

Analysis and Clarification

Dependency Isolation: The test mocks the Jdbi object and the UserDAO interface to avoid interacting with a real database. This isolation ensures that the test focuses solely on the logic of the UserService.
Mockito Interactions: The test uses when() to define the expected behavior of the mocked objects, and verify() to ensure that the expected interactions took place during the test.
Test Coverage: This test ensures that the findUserById method correctly interacts with the mocked dependencies and returns the expected user object.

Additional Value

Testing Different Scenarios: We can extend these tests to cover various scenarios, such as handling exceptions, testing different database query parameters, and validating the returned data.
Integration Tests: While unit tests focus on individual components, integration tests can be used to verify the interactions between different parts of the application, including the JDBI service and the database.
Test-Driven Development (TDD): Writing tests before implementation can guide the development process and ensure that the code is designed for testability.

Conclusion

Testing JDBI services with JUnit 5 and Mockito allows for comprehensive and robust testing. By isolating dependencies and mocking interactions, we can focus on the core logic of the service and ensure its reliability. Following best practices like TDD and covering various scenarios leads to higher quality and maintainable code.

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