What are Testcontainers?
Testcontainers is a JVM library that allows users to run and manage Docker images and control them from Java code. The integration test additionally runs external components as real Docker containers.
- Databases — Run PostgreSQL as a Docker image
- Mocked HTTP server — HTTP services by using MockServer or WireMock Docker images
- Redis — run real Redis as a Docker image,
- Message Brokers — RabbitMQ
- AWS — S3, DynamoDB etc
- Any other application that can be run as a Docker image
How to use?
- Setup : Spring Boot and Junit 5
- Dependency to testImplementation “org.testcontainers:postgresql:1.16.2” and testImplementation “org.testcontainers:junit-jupiter:1.16.2”
- And then some wireing to start testcontainers and link them to the test context so that integration tests knows where to look for the containers.
Example Abstract Class for setup
How to write a test?
Advantages
- Run Integration Tests offline.
- You run tests against real components, PostgreSQL database instead of the H2 database.
- You can mock AWS services.
- Implementation and tests can be written by developers same time when raising a PR.
- Multiple containers can be added and it’s consistent across all developer machines. Same versions etc and runs without any efforts with GitHub actions.
Disadvantages
- The main limitation is, that containers cannot be reused between test classes.
- Adding “one more” external dependency.
- Takes a bit more time than usual to start a container, 4–5 seconds for Postgres VS 0.5 seconds for H2.
- When running locally, local machine should be powerful enough too ;)
- More RAM, More Power as multiple containers can be run.
References
https://www.baeldung.com/spring-boot-testcontainers-integration-test
Originally published at https://www.sameerkulkarni.de on December 7, 2021.
