Test containers for database testing in Spring Boot - Mini Project: Build & Apply

Test containers for database testing

📖 Scenario: You are building a Spring Boot application that needs to test database operations reliably. Instead of using a real database server, you want to use a test container that runs a temporary database during tests. This helps keep tests isolated and easy to run anywhere.

🎯 Goal: Create a Spring Boot test class that uses Testcontainers to start a PostgreSQL database container. Configure the test to connect to this container and verify a simple database connection.

📋 What You'll Learn

Create a PostgreSQLContainer instance with the image postgres:15-alpine

Configure the container to start before tests

Set Spring datasource properties dynamically from the container

Write a simple test method that checks the datasource URL contains jdbc:postgresql

💡 Why This Matters

🌍 Real World

Testcontainers allow developers to run real database instances in containers during automated tests. This ensures tests run consistently on any machine without manual database setup.

💼 Career

Many companies use Testcontainers for integration testing in Java Spring Boot projects. Knowing how to set up and use Testcontainers is valuable for backend developers and QA engineers.

1

Set up PostgreSQLContainer instance

Create a static variable called postgresContainer of type PostgreSQLContainer using the image "postgres:15-alpine". Initialize it with new PostgreSQLContainer<>("postgres:15-alpine").

Spring Boot

# Create a static PostgreSQLContainer variable named postgresContainer
# Your code here

Need a hint?

Use static PostgreSQLContainer<?> postgresContainer = new PostgreSQLContainer<>("postgres:15-alpine") to create the container.

2

Start container before tests

Add a static block to start postgresContainer before any tests run by calling postgresContainer.start() inside the block.

Spring Boot

import org.testcontainers.containers.PostgreSQLContainer;

public class DatabaseTest {
    static PostgreSQLContainer postgresContainer = new PostgreSQLContainer("postgres:15-alpine");

    // Start the container before tests
    static {
        // Your code here
    }
}

Need a hint?

Use a static block static { postgresContainer.start(); } to start the container once.

3

Configure Spring datasource properties dynamically

Create a method annotated with @DynamicPropertySource named registerPgProperties that takes a DynamicPropertyRegistry parameter called registry. Inside, set the properties spring.datasource.url, spring.datasource.username, and spring.datasource.password using registry.add with lambdas returning postgresContainer.getJdbcUrl(), postgresContainer.getUsername(), and postgresContainer.getPassword() respectively.

Spring Boot

import org.testcontainers.containers.PostgreSQLContainer;
import org.springframework.test.context.DynamicPropertyRegistry;
import org.springframework.test.context.DynamicPropertySource;

public class DatabaseTest {
    static PostgreSQLContainer postgresContainer = new PostgreSQLContainer("postgres:15-alpine");

    static {
        postgresContainer.start();
    }

    // Add @DynamicPropertySource method to set datasource properties
    // Your code here
}

Need a hint?

Use @DynamicPropertySource and registry.add with method references to set the datasource properties.

4

Write a test method to verify datasource URL

Add a test method annotated with @Test named testDatasourceUrl. Inject a javax.sql.DataSource parameter named dataSource. Inside, get the connection URL from dataSource.getConnection().getMetaData().getURL() and assert it contains the string "jdbc:postgresql" using org.junit.jupiter.api.Assertions.assertTrue.

Spring Boot

import org.testcontainers.containers.PostgreSQLContainer;
import org.springframework.test.context.DynamicPropertyRegistry;
import org.springframework.test.context.DynamicPropertySource;
import org.junit.jupiter.api.Test;
import javax.sql.DataSource;
import static org.junit.jupiter.api.Assertions.assertTrue;

public class DatabaseTest {
    static PostgreSQLContainer postgresContainer = new PostgreSQLContainer("postgres:15-alpine");

    static {
        postgresContainer.start();
    }

    @DynamicPropertySource
    static void registerPgProperties(DynamicPropertyRegistry registry) {
        registry.add("spring.datasource.url", postgresContainer::getJdbcUrl);
        registry.add("spring.datasource.username", postgresContainer::getUsername);
        registry.add("spring.datasource.password", postgresContainer::getPassword);
    }

    // Add a test method named testDatasourceUrl
    // Your code here
}

Need a hint?

Write a @Test method that gets the connection URL from the injected DataSource and asserts it contains "jdbc:postgresql".