Writing Tests

Guidelines for writing tests in IntelliJ IDEA codebase.

For examples, see community/platform/testFramework/junit5/test/showcase/.

Prefer JUnit 5 over JUnit 4

Use JUnit 5 with @TestApplication annotation instead of extending LightJavaCodeInsightFixtureTestCase.

Why JUnit 5:

• Faster: No class hierarchy overhead, shared fixtures via companion objects
• Cleaner: Annotations (@TestDisposable, @RegistryKey) instead of manual setup/teardown
• Flexible: Mix EDT and non-EDT tests in one class, parameterized tests, nested tests
• Better isolation: Each test gets fresh disposables automatically

Shared Fixtures Pattern

Use companion object fixtures shared between all tests: