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React Native · Question Set
Testing, Deployment & CI/CD interview questions for placements and exams.
Questions
14
Included in this set
Subject
React Native
Explore more sets
Difficulty
Mixed
Level of this set
Go through each question and its explanation. Use this set as a focused practice pack for React Native.
Jest is a testing framework developed by Meta for unit and snapshot testing in JavaScript and React Native apps. It provides built-in mocking, code coverage, and a zero-config setup for fast feedback.
test('renders correctly', () => { const tree = renderer.create(<App />).toJSON(); expect(tree).toMatchSnapshot(); });For complete preparation, combine this set with full subject-wise practice for React Native. You can also explore other subjects and sets from the links below.
Detox is used for end-to-end (E2E) testing in React Native. It automates user interactions on real devices or emulators. It ensures the entire app flow works as expected — from UI to backend communication.
Snapshot testing ensures that the output of a component hasn’t changed unexpectedly. When a UI change is intentional, developers must update the stored snapshot manually.
jest.mock() replaces real modules or dependencies with fake ones for isolated testing. This helps test components without performing actual API calls or file reads.
jest.mock('axios', () => ({ get: jest.fn() }));The detox test command launches the testing environment, builds the app, and runs all configured E2E tests. You can specify a configuration to target Android or iOS builds individually.
GitHub Actions provides a YAML-based CI/CD workflow directly inside the repository. You can automate testing, building, and deployment for React Native apps across Android and iOS targets.
Environment variables are usually stored in .env files and accessed using libraries like react-native-dotenv. This helps separate sensitive data like API keys from source code.
The first step in a CI/CD pipeline is to fetch the project repository code. Subsequent steps like build, test, and deploy run sequentially on the freshly cloned codebase.
Jest focuses on unit and snapshot testing of individual components or functions. It runs entirely in JavaScript and doesn’t require a simulator. Detox performs end-to-end testing by running real user flows on actual devices or emulators. It validates the integration of components and APIs together.
CI/CD ensures continuous integration of code changes and automated delivery to testers or app stores. It improves team collaboration, reduces manual errors, and speeds up release cycles through automation and consistent build validation.
First, make JavaScript or asset changes and bundle them using the React Native CLI. Then, use the appcenter CLI to push the update to CodePush servers. The next time the user opens the app, CodePush downloads and applies the update automatically without requiring reinstallation.
Jest can generate coverage reports using the --coverage flag, showing which files or lines are untested. Developers can then write additional unit or integration tests to cover untested branches, ensuring stable codebases before deployment.
First, generate a release build for both Android and iOS. Then, sign the builds using production keys. Next, upload them to Google Play and Apple App Store. You can later use CodePush for small over-the-air updates between releases.
CodePush allows developers to update JavaScript bundles and assets directly to users’ devices. It avoids waiting for app store approval while still respecting app store policies for non-native updates.