React Native / Expo Testing

This file extends common/testing.md with React Native / Expo specific content. Coverage target and TDD workflow are inherited from common/testing.md (80% minimum, RED-GREEN-REFACTOR).

Tooling

Layer	Tool
Unit / component	Jest + `@testing-library/react-native` (via `jest-expo` preset)
Hooks	`@testing-library/react-native` `renderHook`
E2E	Maestro (recommended, simple YAML flows) or Detox
Type safety	`tsc --noEmit` in CI

Component Tests

Query by accessible role/label/text, not by testID unless necessary — this also enforces accessibility.
Assert on user-visible behavior, not implementation details.
Follow Arrange-Act-Assert.

tsx

import { render, screen, fireEvent } from '@testing-library/react-native'

test('calls onSelect with the user id when pressed', () => {
  const onSelect = jest.fn()
  render(<UserCard user={{ id: '1', email: 'a@b.com' }} onSelect={onSelect} />)

  fireEvent.press(screen.getByText('[email protected]'))

  expect(onSelect).toHaveBeenCalledWith('1')
})

Mocking

Mock Expo SDK modules (camera, location, notifications, secure-store) at the test boundary.
Wrap components that use TanStack Query in a QueryClientProvider with a fresh client per test.
Mock navigation (expo-router) so screens render in isolation.

E2E

Cover critical flows only: auth, primary navigation, core transactions.
Run E2E on CI against a built app (EAS Build) before release.

What to test first

Use the tdd-guide agent proactively for new features: write a failing test that captures the behavior, then implement.