**Introduction** When a single codebase powers both a web app and a mobile app, maintaining consistency and reliability becomes challenging. A unified testing strategy helps you catch regressions early, reduce maintenance overhead, and ensure a smooth user experience across platforms. This guide outlines practical steps to set up an integrated test environment that works for both React Web and React Native. **Key Benefits** - **Consistent quality** – Shared test suites enforce the same behavior on web and mobile. - **Faster feedback loops** – CI pipelines can run all tests in parallel, giving instant results. - **Reduced duplication** – Common utilities, mocks, and configurations live in one place. - **Better coverage insights** – Consolidated coverage reports highlight gaps across platforms. **Core Testing Tools** - **Unit testing** – Jest is the de‑facto standard. Configure a single `jest.config.js` that extends for both environments. - **Component testing** – React Testing Library lets you test components as users interact with them. It works identically for web and React Native. - **End‑to‑end testing** – Cypress for web and Detox (based on Jest) for React Native. Both can be invoked from the same script. - **Visual regression** – Storybook’s addon “storybook-addon-react-native” enables visual checks for native components alongside web stories. **Building a Shared Test Config** 1. Create a root `jest.config.js` that exports different roots and clearable modules per environment. 2. Use a common set of helper functions (e.g., `render` wrapper) that internally call `react-dom/render` or `react-native-renderer` based on a small flag. 3. Define shared mock files (like `__mocks__/fetchMock.js`) that can be required in both platforms. 4. Add a `scripts` object in `package.json` that runs `npm test:web` and `npm test:mobile` from a single `test` command. **Running Tests in CI** ```json "scripts": { "test:web": "jest --config=jest.web.config.js", "test:mobile": "jest --config=jest.native.config.js", "test:e2e:web": "cypress run", "test:e2e:mobile": "detox test --configuration ios.sim.debug", "test": "npm run test:web && npm run test:mobile && npm run test:e2e:web && npm run test:e2e:mobile" } ``` Integrate these scripts into your CI platform (GitHub Actions, GitLab CI, etc.) so each push triggers all four test suites. **Best Practices** - Keep test data platform‑agnostic; store fixtures in JSON files and load them via a shared utility. - Use environment variables to toggle platform‑specific behavior (e.g., `PLATFORM=web`). - Leverage parallel execution for Jest and Cypress to shorten run times. - Regularly review coverage reports and aim for overlapping coverage where logic is shared. - Document any platform‑specific quirks (e.g., touch events vs. mouse events) in a shared wiki. **Getting Started Checklist** - [ ] Install Jest, React Testing Library, Cypress, Detox, and Storybook. - [ ] Create a unified `jest.config.js` and split configurations for web/native. - [ ] Build a reusable `render` helper that abstracts the renderer. - [ ] Add a simple unit test and a component test to verify the setup. - [ ] Configure CI scripts and enable parallel job execution. - [ ] Run a full test suite locally and in CI to confirm no regressions. **Conclusion** A well‑planned, integrated testing approach reduces duplication, improves confidence, and accelerates development across React Web and React Native. By sharing configs, utilities, and CI pipelines, teams can focus on building features rather than maintaining separate test stacks.