import static org.junit.jupiter.api.Assertions.*;
import org.junit.jupiter.api.*;
import java.sql.*;
class User {
private int id;
private String name;
private String email;
public User(int id, String name, String email) {
this.id = id;
this.name = name;
this.email = email;
}
public int getId() { return id; }
public String getName() { return name; }
public String getEmail() { return email; }
}
class UserRepository {
private Connection connection;
public UserRepository(Connection connection) {
this.connection = connection;
}
public void save(User user) throws SQLException {
String sql = "INSERT INTO users (id, name, email) VALUES (?, ?, ?)";
try (PreparedStatement stmt = connection.prepareStatement(sql)) {
stmt.setInt(1, user.getId());
stmt.setString(2, user.getName());
stmt.setString(3, user.getEmail());
stmt.executeUpdate();
}
}
public User findById(int id) throws SQLException {
String sql = "SELECT id, name, email FROM users WHERE id = ?";
try (PreparedStatement stmt = connection.prepareStatement(sql)) {
stmt.setInt(1, id);
try (ResultSet rs = stmt.executeQuery()) {
if (rs.next()) {
return new User(rs.getInt("id"), rs.getString("name"), rs.getString("email"));
} else {
return null;
}
}
}
}
}
public class InMemoryDatabaseTest {
private Connection connection;
private UserRepository userRepository;
@BeforeEach
void setUp() throws SQLException {
connection = DriverManager.getConnection("jdbc:h2:mem:testdb;DB_CLOSE_DELAY=-1");
try (Statement stmt = connection.createStatement()) {
stmt.execute("CREATE TABLE users (id INT PRIMARY KEY, name VARCHAR(255), email VARCHAR(255))");
}
userRepository = new UserRepository(connection);
}
@AfterEach
void tearDown() throws SQLException {
try (Statement stmt = connection.createStatement()) {
stmt.execute("DROP TABLE users");
}
connection.close();
}
@Test
void testSaveAndFindUser() throws SQLException {
User user = new User(1, "Alice", "alice@example.com");
userRepository.save(user);
User retrieved = userRepository.findById(1);
assertNotNull(retrieved, "Retrieved user should not be null");
assertEquals("Alice", retrieved.getName(), "User name should match");
assertEquals("alice@example.com", retrieved.getEmail(), "User email should match");
}
}
The test class InMemoryDatabaseTest uses JUnit 5 to test database operations on an in-memory H2 database.
Setup: The @BeforeEach method creates a fresh in-memory database and a users table before each test. This ensures tests are isolated and repeatable.
Teardown: The @AfterEach method drops the table and closes the connection to clean up resources.
Test: The testSaveAndFindUser method saves a User object and then retrieves it by ID. Assertions check that the retrieved user is not null and that the name and email match the expected values.
This approach uses explicit SQL and JDBC to keep the example simple and clear for beginners. It follows best practices like resource management with try-with-resources and clear assertion messages.
