testing

name	testing
description	Guidance for testing React Native code — unit tests for logic, component tests for behaviour, E2E for critical paths, and edge-case coverage. Use when adding tests, reviewing test quality, or setting a coverage bar.
version	1.0.1
platforms	["ios","android"]
react-native-version	0.76+
tags	["react-native","testing","quality"]

Testing Skill

Applicability

• Platforms: iOS and Android
• React Native: 0.76+ (New Architecture interop assumed unless a checklist item says otherwise)

When to Use

• Adding tests for a new feature, hook, or utility
• Reviewing whether a change is adequately tested before merge
• Deciding what to test and at which level
• Investigating a regression that tests should have caught

Guidance

What to Test

• Unit tests for hooks and utility functions
• Component tests for user-facing behaviour, not implementation details
• End-to-end flow for each critical path (e.g. with Maestro), where applicable
• Edge cases covered: empty data, error state, offline, large data sets

How to Test

• Mocks are minimal — prefer real implementations where practical
• No snapshot tests as a primary assertion (brittle, low signal)
• Tests assert observable behaviour and outputs, not internal calls
• Each test is independent and does not rely on execution order

Incorrect:

// Asserts an implementation detail — breaks on harmless refactors
expect(component.find('useFetchUsers')).toHaveBeenCalled();

Correct:

// Asserts what the user sees
render(<UserList />);
expect(await screen.findByText('Ada Lovelace')).toBeOnTheScreen();

Pitfalls

• Snapshot tests fail on every harmless markup change, training the team to update them without reading — they catch little and erode trust.
• Over-mocking produces tests that pass while the real integration is broken; mock only what you must (network, native modules).
• Testing implementation details (which hook ran, internal state) makes refactoring painful even when behaviour is unchanged.
• Skipping edge cases (empty, error, offline) leaves the exact states users hit in production untested.