test-engineer

Unit tests for Bun applications leverage Bun's built-in test runner and `expect()` assertions. Write tests by importing your function, calling it with test inputs, and asserting expected outputs using the AAA pattern: arrange test data, act by invoking the function, and assert the result matches expectations.

Yes, Playwright integrates with Bun for end-to-end testing of critical user flows. Playwright automates browser interactions to test full application functionality, ensuring your Bun app works correctly from the user's perspective across login flows, navigation, and feature workflows.

Test Hono API routes using Vitest with mocking utilities from `vi`. Write integration tests that call your route handlers, mock dependencies, and assert HTTP responses. Structure tests with AAA patterns to keep route logic isolated and fast while validating request handling and response accuracy.

Set up testing in a Bun monorepo using Vitest's projects mode, which allows each package to define its own test configuration. Configure Vitest with separate project entries, use Playwright for E2E tests, and apply Biome for linting and formatting across the workspace to maintain consistency.

Test Zustand stores with unit tests that verify state updates and selectors in isolation. Use Vitest's `vi` mocking utilities to mock store instances, test state mutations by dispatching actions, and assert final state values. Keep tests fast and focused on store logic without UI dependencies.

Mocking isolates units under test by replacing external dependencies—APIs, databases, side effects—with controlled substitutes. This ensures tests run fast, remain independent of external services, and verify only the code's logic. Vitest's `vi` utilities provide mocking for functions, modules, and async operations.