Today I’ll show you a way to write integration tests for your Spring Boot based application with a real database (meaning not mocked or in-memory) and not an embedded database like H2. In the last weeks, I was looking for a solution to write integration tests for my Spring Data based application which was using a Postgres database. I had the following requirements for this task:
- The integration tests should use the same database as in production (referring to the Twelve-Factor App I wanted to keep my environment during the tests as similar as possible to the production environment)
- The tests should not need any pre-setup before running (e.g. like manually setting up a test database)
- The tests should be able to be parallelized
- The tests should use my Flyway DDL scripts and create-drop (
spring.jpa.hibernate.ddl-auto) shouldn’t be activated for my tests - Good integration with the excellent Spring tests environment
For this task, I found the awesome project:Â Testcontainers. The project describes itself as the following:
“Testcontainers is a Java library that supports JUnit tests, providing lightweight, throwaway instances of common databases, Selenium web browsers, or anything else that can run in a Docker container.”
Setup Testcontainers in Spring Boot project
For using this dependency you need to have Docker on your local machine/on your build server (Jenkins etc.). With this project, you can use a @ClassRule or @Rule on each of your integration tests and define the Docker image for your test. For MySQL and Postgres and there are already built-in solutions but you are free to use the image of your choice like the following:
1 2 3 4 5 6 7 8 | // generic container for self-defined Docker images @ClassRule public static GenericContainer redis = new GenericContainer("redis:3.0.6").withExposedPorts(6379); // built-in containers @ClassRule public static PostgreSQLContainer postgreSQLContainer = new PostgreSQLContainer().withPassword("inmemory") .withUsername("inmemory"); |
To meet my third requirement (The tests should be able to be parallelized) I configured the maven-surefire-plugin to run my test classes in parallel and every Postgres container will use a random port.
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 | <build> <plugins> <plugin> <groupId>org.springframework.boot</groupId> <artifactId>spring-boot-maven-plugin</artifactId> </plugin> <plugin> <groupId>org.apache.maven.plugins</groupId> <artifactId>maven-surefire-plugin</artifactId> <configuration> <parallel>classes</parallel> <threadCount>2</threadCount> </configuration> </plugin> </plugins> </build> |
Adjust integration test to use Testcontainers
Overriding the properties for your application during the tests is as easy as the following snippet:
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 | @RunWith(SpringRunner.class) @SpringBootTest(webEnvironment = SpringBootTest.WebEnvironment.RANDOM_PORT) @ContextConfiguration(initializers = IntegrationTest.Initializer.class) public class IntegrationTest { @ClassRule public static PostgreSQLContainer postgreSQLContainer = new PostgreSQLContainer().withPassword("inmemory") .withUsername("inmemory"); public static class Initializer implements ApplicationContextInitializer<ConfigurableApplicationContext> { @Override public void initialize(ConfigurableApplicationContext configurableApplicationContext) { TestPropertyValues values = TestPropertyValues.of( "spring.datasource.url=" + postgreSQLContainer.getJdbcUrl(), "spring.datasource.password=" + postgreSQLContainer.getPassword(), "spring.datasource.username=" + postgreSQLContainer.getUsername() ); values.applyTo(configurableApplicationContext); } } } |
If you use the @SpringBootTest annotation to spin-up the whole Spring container and the embedded Tomcat your Flyway scripts will be executed against the container and you verify them as a side-effect. Adding the @Sql annotation to a test method you can execute further SQL scripts before your tests and add e.g. sample data before your test. These changes will get rolled back after your test method exists.
1 2 3 4 5 6 7 8 9 10 11 | @Test @Sql("/insertPersons.sql") public void testRestEndpointForAllPersons() { ResponseEntity<Person[]> result = testRestTemplate.getForEntity("http://localhost:" + localPort + "/persons", Person[].class); assertNotNull(result); assertThat(result.getBody().length, is(4)); } |
For a full example with a sample Spring Boot application (simple CRUD REST application) visit my GitHub repository and have a look at the tests. I created three integration test classes (s (definitely not a best practice for your enterprise project) for creating, reading and deleting an entity to show you the parallel execution of the tests.
Happy integration-testing with Spring Boot and Testcontainers!
2 comments
Hi! Thank you for an awesome article. It is really useful tips for anyone who wants to do integration testing for Spring Boot applications.
Actually, there is a really suitable open-source library for Spring Boot, which makes integration testing with containers even more easy – https://github.com/Playtika/testcontainers-spring-boot
Hi Oleksandr, thanks for the link!