| Test structure | describe('suite', () => {}) | Organize related tests |
| Single test | test('behavior', () => {}) or it() | Both are aliases |
| Parameterized tests | test.each([...])('name', (arg) => {}) | Run same test with different inputs |
| Concurrent tests | test.concurrent('name', async () => {}) | Run tests in parallel |
| Skip test | test.skip('name', () => {}) or skipIf(cond) | Conditionally skip tests |
| Only test | test.only('name', () => {}) | Run specific test for debugging |
| Assertions | expect(value).toBe(expected) | Compare primitive values |
| Deep equality | expect(obj).toEqual(expected) | Compare objects/arrays |
| Async assertions | await expect(promise).resolves.toBe(value) | Test promise resolution |
| Before each test | beforeEach(() => {}) | Setup before each test |
| After each test | afterEach(() => {}) | Cleanup after each test |
| Mock function | vi.fn() | Create spy function |
| Mock module | vi.mock('./module') | Replace entire module |
| Spy on method | vi.spyOn(obj, 'method') | Track calls to existing method |
| Clear mocks | vi.clearAllMocks() | Clear call history |
| Fake timers | vi.useFakeTimers() | Control setTimeout/setInterval |
| Render component | render(<Component />) | Mount React component for testing |
| Query by role | screen.getByRole('button') | Find elements by accessibility role |
| User interaction | await user.click(element) | Simulate user events |
| Wait for change | await waitFor(() => expect(...)) | Wait for async changes |
| Find async element | await screen.findByText('text') | Query + wait combined |
| Render hook | renderHook(() => useHook()) | Test custom hooks |
| Update hook props | rerender(newProps) | Re-render hook with new props |
| Snapshot | expect(value).toMatchSnapshot() | Compare against saved snapshot |
| Inline snapshot | expect(value).toMatchInlineSnapshot() | Snapshot stored in test file |
| CLI run once | vitest run | Single run, no watch |
| Run changed tests | vitest --changed | Tests affected by git changes |
| Filter by name | vitest -t "pattern" | Grep test names |
| Soft assertions | expect.soft(value).toBe(x) | Continue on failure, collect all |
| Poll assertions | await expect.poll(() => val).toBe(x) | Retry until passing |
| Test fixtures | const test = base.extend<F>({...}) | Reusable setup via test.extend |
| Hoisted mocks | vi.hoisted(() => ({ fn: vi.fn() })) | Variables for vi.mock factory |
| Shard tests | vitest --shard 1/3 | Split across CI workers |
| Tags | test('name', { tags: ['slow'] }, ...) | Filter with --tags-filter |
| Stub globals | vi.stubGlobal('fetch', vi.fn()) | Replace global objects cleanly |
