React Native is a framework for cross-platform mobile app development for iOS and Android. React Native is the ideal business solution but humans make mistakes. Some small errors and edge cases can cascade into larger failures. In some cases, bugs lead to bad user experience and ultimately, business losses. So testing is important because it helps you uncover these mistakes and verifies that your code is working. Let’s explore some types of testing for React Native apps and a list of useful testing tools for the framework.
Types of testing for React Native apps
Writing tests. To start with tests, you first need to write code that is testable. Instead of writing your entire program in one huge file with many lines of code, you write your code in multiple small modules that you can test more thoroughly than if you tested the assembled whole. In this way, writing testable code is intertwined with writing clean, modular code. After writing testable code, it’s time to write some actual tests!
Unit tests. Unit tests cover the smallest parts of code, like individual functions or classes. This includes testing JavaScript objects and methods which are present at the component level.
Component tests. React components are responsible for rendering your app, and users will directly interact with their output. Even if your app’s business logic has high testing coverage and is correct, without component tests you may still deliver a broken UI to your users. Therefore, there are two things you may want to test are interaction and rendering for testing React components.
Integration tests. When writing larger software systems, individual pieces of it need to interact with each other. In integration testing, real individual units are combined (same as in your app) and tested together to ensure that their cooperation works as expected.
End-to-End tests. In End-to-End tests (E2E tests), you no longer think about React components, React Native APIs, Redux stores or any business logic. That is not the purpose of E2E tests and those are not even accessible to you during E2E testing. You only must verify your app is working as expected on a device (or a simulator/emulator) from the user perspective.
Top 5 React Native testing tools
Automated testing is the best way to ensure your app works as expected, ranging from static analysis to end-to-end tests. Below are the top 5 React Native testing tools that you can use for React Native apps.
1. Jest
Jest is a JavaScript testing framework that works with simplicity. It is a testing framework that is used to solve the issues in the JavaScript codebase. Jest lets you access the DOM via jsdom. While jsdom is only an approximation of how the browser works, it is often good enough for testing React components. Jest provides a great iteration speed combined with powerful features like mocking modules and timers so you can have more control over how the code executes.
The developers of Facebook have developed Jest that works with React Native on a default basis. One of the attractive features of Jest is Snapshot testing. Jest comes with great official docs and by following the guide, you will be able to run it fast. Jest is also the tool recommended on React Native docs.
*Features of Jest are:
- Fast and Safe
- Mock by default makes testing much simpler
- Out of the box code coverage
- Jest Snapshot testing that simplifies the testing process
2. Detox
Detox is an end-to-end (E2E) testing library which is used for apps built on React Native. By using it, you can emulate the behavior of the users and test your apps automatically to know how the users react to it. It also supports permissions different device configurations, notifications and everything which the user may wish to do with the app.
Detox was developed from scratch to support the projects of React Native as well as the other pure native ones. It tests mobile apps while it is running on the simulator or real mobile device and interacts with it just like any user. When it comes to automated testing E2E remains as the core problem due to its flakiness.
*Features of Detox are:
- Works in complete sync with the app
- Easy to be connected to any CI systems
- For Gray box testing
- Independent test runner
3. Jasmine
Jasmine is a development framework that is behavior-driven and is used to test JavaScript code. It does not need a DOM and does not have a dependency on any other JavaScript frameworks. It comes with a clean syntax which makes it easy to write tests. It is an open-source framework which can be made easily available for different versions like ruby gem, stand-alone, Node.js,…
*Features of Jasmine are:
- Not need to have DOM
- Behavior-driven development framework used to test JavaScript code
- Works on a platform which is JavaScript enabled
- Unit testing frameworks highly influence it
4. Karma
Karma aims at developing a productive testing environment for the developers. Such a situation will be focused on saving the developers from a large number of configurations and just letting them write the code for the tests and get instant feedback. Getting such instantaneous feedback will make the developers more creative and productive.
*Features of Karma are:
- Open-source
- Remote control
- Test on real devices or on real browsers
- Easy debugging via WebStorm or your IDE or Google Chrome.
- Continuous integration
5. Appium
Appium is an open-source tool that is used for automating mobile web, native and hybrid applications on Android mobile, iOS mobile, and Windows desktop platforms. Appium support cross-platform testing and so you can write tests using a single API and then run them against multiple platforms. In short, Appium makes the code reuse among different test suites possible.
*Features of Appium are:
- Open-source
- Free test automation tool used for mobile applications
- Write tests with dev tools using any WebDriver-compatible language
- Use any testing framework
- Switch seamlessly between native app automation and WebView automation
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*Reference:
- https://reactnative.dev/docs/testing-overview
- https://medium.com/@ronak8036/react-native-testing-tools-f38d715adb57
- https://technologywire.net/best-tools-for-testing-native-mobile-apps/
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