Integration Testing with TestContainers

Ottawa Java User Group presentation. September 28, 2017.

Transcript

1. Integration Testing with TestContainers Aleksey Vorobyov Ottawa Java User Group September 28, 2017
2. Why integration tests are important • 1st test in Real World ◦ Modern [micro]service works with a lot of other services ◦ Points of integration are sources of failures • Isolation. Errors from other services don’t affect a system under test. ◦ In system tests it takes more time to understand a root cause
3. Use real resources • Databases ◦ Embedded databases like H2 don’t really test anything • Files • Other services (HTTP mocks) • Message queue middleware • Networking
4. Advantages of integration tests • Real world testing • Isolated verification. Other services are under control. • Find issues before deployment • Can be used on a developer machine ◦ Sometimes it’s too hard to run System Tests on a developer machine
5. Disadvantages • Complexity. Unit tests usually are simpler. • Slower than unit tests
6. Ways to run integration tests • Install services locally • Provision embedded services from tests • Use VM/Vagrant Disadvantages • Dev machine pollution • Hard to run/manage/cleanup tests on CI especially in parallel
7. TestContainers library 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.
8. Problems TestContainers solves • Integration tests isolation ◦ Containers/Services from different tests are isolated ◦ Containers use random ports on a host machine ◦ Tests can be started on the same machine in parallel without port conflicts • Cleanup containers on JVM shutdown ◦ CI servers are always in a predictable state • Hides verbose container management commands behind developer friendly tools (Java code)
9. TestContainers use cases • Data Repository tests ◦ Start a database container ◦ Configure a repository datasource ◦ Test repository methods • Integration tests ◦ Start dependent services in containers ◦ Configure a service under test ◦ Test the service API • UI/Acceptance tests ◦ Provision whole System ◦ Test an application using UI/Acceptance tools
10. How to use TestContainers @ClassRule public static GenericContainer redis = new GenericContainer("redis:3") .withExposedPorts(6379); Then redis.getContainerIpAddress() redis.getMappedPort(6379) returns a binded random port on localhost
11. Example. Service Integration Testing
12. Example. UI/Acceptance Test
13. Example. System Test • Uses Docker compose • Not suitable for big Systems
14. Example. Run inside CI node Run tests from inside another docker instance docker run -v /var/run/docker.sock:/var/run/docker.sock