frontend-test

Use Vitest's describe/it/expect API to test pure functions with normal, exception, and boundary cases. Place tests in a __tests__ directory next to the source file, named calculator.test.ts, and run them with npx vitest run.

Wrap the component in ConfigProvider and App context before rendering with @testing-library/react. Then query elements with screen.getByText or getByRole and simulate interactions using @testing-library/user-event.

Vitest integrates natively with Vite as the test runner, paired with @testing-library/react for component rendering, @testing-library/jest-dom for DOM assertions, jsdom for the browser environment, and Playwright for E2E tests.

Use renderHook from @testing-library/react to mount the hook, then wrap state updates in act() and assert on result.current. This avoids calling the hook outside a component, which React forbids.

Yes, mock globalThis.fetch with vi.fn() to simulate resolved JSON responses and rejected network errors. Tests must never make real network requests so they run offline and produce no side effects.

Skip tests for pure configuration files like vite.config.ts, third-party library internals, and visual styling without screenshot requirements. Backend NestJS code should use a dedicated backend testing approach instead.