Instruction file imported from chogng/ash (.github/instructions/writing-tests.instructions.md). Copyright stays with the author.

Writing Tests

Canonical reference: https://github.com/microsoft/vscode/wiki/Writing-Tests

Test Types

Running Tests

• Unit tests: corepack pnpm --dir ash-ts test:unit
  • Filter: --grep <pattern>
  • File: --run src/ash/<owner>/test/<runtime>/myFile.test.ts
  • Glob: --runGlob '**/myFile.test.js'
• Editor browser integration: corepack pnpm --dir ash-ts test:editor:browser
• Browser and Electron UI: use the owning test:smoke:* Playwright project.

Writing Unit Tests

Tests use Mocha's TDD interface (suite/test) with node:assert/strict. Import Mocha functions explicitly; use injected test doubles for dependencies.

Clean Teardown

Keep disposables with the test that creates them. Use using for synchronous ownership and try/finally for asynchronous cleanup:

import { suite, test } from 'mocha';

suite('MyComponent', () => {
	test('releases its listener', () => {
		using component = new MyComponent();
		// Assert the behavior and lifecycle contract.
	});
});

Restore any test-owned mock or global change in the same test. File-level resources use Mocha's suiteTeardown and must be released before the test file finishes.

Best Practices

• Minimize assertions per test — prefer one assert.deepStrictEqual snapshot over many fine-grained assertions
• Don't add tests to the wrong suite — find the relevant suite block
• Follow suite/test consistently within a file
• Don't stub globals (e.g., (mainWindow as any).X = ...) — make dependencies injectable instead

Snapshot Testing

When an existing snapshot baseline covers the behavior, update it in the same change and review the diff. Otherwise assert the owned behavior directly.