Test containers for database testing in JUnit - Cheat Sheet & Quick Revision

Recall & Review

beginner

What is a test container in database testing?

A test container is a lightweight, disposable instance of a database or service that runs in a container during tests. It helps create a real environment for testing without affecting the developer's machine or production data.

intermediate

Why use test containers instead of an in-memory database for testing?

Test containers run the actual database software in a container, providing a more realistic environment. In-memory databases may behave differently from real databases, so test containers catch issues that only appear in real setups.

intermediate

How do you start a PostgreSQL test container in JUnit 5?

You use the @Testcontainers annotation on the test class and define a static PostgreSQLContainer<?> field with @Container. The container starts before tests and stops after.

beginner

What is the benefit of using @Container annotation in JUnit tests?

The @Container annotation manages the lifecycle of the container automatically, starting it before tests and stopping it after, so you don't have to write manual setup or teardown code.

advanced

What should you consider about test container resource usage?

Test containers use system resources like CPU, memory, and disk. Running many containers or large databases can slow tests. It's good to reuse containers or limit parallel tests to keep tests fast.

What does a test container provide in database testing?

A A mock object for database calls

B An in-memory database simulation

C A real database instance running in a container

D A cloud-hosted database service

Test containers run the actual database software inside a container, providing a real instance for testing.

Which annotation in JUnit 5 is used to mark a test container field?

A @Container

B @TestContainer

C @Testcontainers

D @BeforeAll

The @Container annotation marks a container field to be managed by JUnit 5 lifecycle.

Why might test containers be preferred over in-memory databases?

A They use less memory

B They provide a real database environment

C They are faster to run

D They require no setup

Test containers run the real database software, giving a more accurate test environment.

What happens to a test container after the tests finish?

A It remains running for reuse

B It is converted to a permanent database

C It crashes intentionally

D It is stopped and removed automatically

Test containers are stopped and removed automatically to keep the environment clean.

Which of these is a common database supported by test containers?

A PostgreSQL

B Oracle Database

C Microsoft Access

D SQLite

PostgreSQL is widely supported and commonly used with test containers.

Explain how test containers improve database testing compared to traditional methods.

Think about how real environment and isolation help testing.

Describe the steps to set up a PostgreSQL test container in a JUnit 5 test class.

Focus on annotations and container lifecycle.