Light and Heavy Tests
Plugin tests run in a real, rather than mocked, IntelliJ Platform environment and use real implementations for most application and project services.
Loading and initializing all the project components and services for a project to run tests is a relatively expensive operation, and we want to avoid doing it for each test. Dependently on the loading and execution time, we make a difference between light tests and heavy tests available in the IntelliJ Platform test framework:
Light tests reuse a project from the previous test run when possible.
Heavy tests create a new project for each test.
Light and heavy tests use different base classes or fixture classes, as described below.
Light Tests
The standard way of writing a light test is to extend the following classes:
BasePlatformTestCase(2019.2 and later) for tests that don't have any Java dependencies. For plugins using pre-2019.2 versions useLightPlatformCodeInsightFixtureTestCase.LightJavaCodeInsightFixtureTestCase(2019.2 and later) for tests that require the Java PSI or any related functionality. For plugins using pre-2019.2 versions useLightCodeInsightFixtureTestCase.
When writing a light test, you can specify the project's requirements that you need to have in your test, such as the module type, the configured SDK, facets, libraries, etc. You do so by extending the LightProjectDescriptor class and returning your project descriptor (usually stored in static final field) from getProjectDescriptor().
If your plugin builds on top of Java support, please see How to test a JVM language? to set up your test environment to obtain the required Mock JDK automatically.
Before executing each test, the project instance will be reused if the test case returns the same project descriptor as the previous one or recreated if the descriptor is different (equals() = false).
Heavy Tests
The setup code for a multi-module Java project looks something like that: