In most cases, once you have the necessary files copied to the test project and loaded into the in-memory editor, writing the test itself involves invoking your plugin code and has few dependencies on the test framework. However, for many common cases the framework provides helper methods that can make testing easier:

• type() simulates the typing of a character or string into the in-memory editor.
• performEditorAction() simulates the execution of an action in the context of the in-memory editor.
• complete() simulates the invocation of code completion and returns the list of lookup elements displayed in the completion list (or null if the completion had no suggestions or one suggestion which was auto-inserted).
• findUsages() simulates the invocation of 'Find Usages' and returns the found usages.
• findSingleIntention() in combination with launchAction() simulate the invocation of an intention action or inspection quickfix with the specified name.
• renameElementAtCaret() or rename() simulate the execution of a rename refactoring.

To compare the results of executing the action with the expected results, you can use the checkResultByFile() method. The file with the expected results can also contain markup to specify the expected caret position or selected text range. If you're testing an action which modifies multiple files (a project-wide refactoring, for example), you can compare an entire directory under the test project with the expected output using PlatformTestUtil.assertDirectoriesEqual().