Today businesses are more inclined towards building cross-platform mobile apps using React Native. Such apps are readily available across all the major mobile app platforms with ease. This saves them a lot of time and money that they would have otherwise spent on developing individual apps for different platforms. When it comes to building business apps, quality always remains as the top priority. Today user expectations are getting higher every year and they are very clear about the app reviews. This means it will not take much time to know whether they like or hate an app available on the app store.

With mobile usage increasing than ever it becomes important for app developers and businesses to build the app the right way and ensure it works across different devices smoothly. Compatibility with different OS versions, chipsets, resolutions and hardware requirements are some of the areas to cover for sure. Keeping everything in mind offering unmatched user experience becomes a challenging task.

This is where you need the right testing tools for the React Native project. In order to find bugs and issues faster and resolve them at the lighting speed automation testing is said to be better.

Challenges for React Native App Testing

Very Complex Setup

In case of React Native debug apps the JavaScript code is completely bundled by using a React Native Packager. This means the task of launching and terminating the packager has to be done too. There are some frameworks where you need to run their services in the background.

So in case of some frameworks, React Native Detox code which is used for the automation of UI is placed in both platform-specific files and JavaScript files. So when it comes to handling the npm/yarn dependencies and resolving issues of the platform-specific libraries, it creates a complete mess.

Recognizing view elements

In case of React Native Development, it offers a feature where all views are generated for both the platforms using JavaScript code automatically. Now, this looks convenient but when it comes to writing some test scripts by making use of native frameworks, there can be a difference in terms of view hierarchy inspected on Android and iOS.

Dealing with app permissions

One of the issues you will come across during testing is handling app permissions. You need to be sure that each test is launched individually and the execution will not be messed up with the permission pop up. There are a lot of plugins available to take care of this issue for native scripts. There are some hybrid frameworks too which can take care of this issue.

Shared state

In some situations, the local databases and app states are shared between some separate tests. So for the people who are working on UI testing automation, it can create issues. So to take care of the app states shared between tests you can choose to go for platform-specific approaches or go ahead to implement custom methods which can clear memory files or cache or any other data. The frameworks dedicated to React Native also cover this issue.

Types of Mobile App Testing

The composition is the base of mobile software development. This means a number of smaller components of software come together to form a bigger one. The bigger one possesses greater functionality in order to achieve the goal of the app. The right practice to run tests for a mobile application is to cover functionality at every level.

The different types of testing followed for React Native apps are:

Unit testing:

This is the basic kind of testing followed for mobile apps. This includes testing JavaScript objects and methods which are present at the component level.

Component testing:

It is possible to test each of the components functionally or visually. In order to test React components, ReactTestUtils offers a simple framework.

Integration testing:

The next comes is integration testing. In this phase, a bunch of different units are tested together as one component or entity.

Functional testing:

This is a kind of black-box testing which is focused on user interactions and requirements. It covers all the user interactions, underlying software the application as a single entity.

List of different React Native testing tools

Jest

Jest is a JavaScript testing framework that works with simplicity. It is a testing framework which is used to solve the issues in the JavaScript codebase. This is result oriented and lets you write tests which are familiar, approachable and with feature-rich API. It is well-documented, can be extended and needs fewer configurations.

The developers of Facebook have developed this and it 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. It enjoys 24953 stars on GitHub.

Features of Jest are:

Fast and safe:

Jest can run tests in parallel reliably all the while ensuring a single global state for tests. In order to make things move faster, Jest runs the failed tests first and based on how long test files take, and it re-organized runs.

Code coverage:

By adding the flag coverage generate code coverage. There is no need for any additional setup. Jest can collect code coverage information including the untested files from the entire projects.

Easy mocking:

Jest can mock any object outside the scope of the test in a simple manner. For the same, it uses custom resolver for imports within the test. In order to spy on function calls which come with readable test syntax, you can make use of imports that are mocked with rich Mock Functions API.

Detox

Detox is an end-to-end testing library which is used for apps build 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. This is where Detox comes into the picture. It enjoys 4455 stars on GitHub.

Pros of Detox

· Works in complete sync with the app

· It is JavaScript-focused

· Developed by Wix for React Native

· For Gray box testing

Cons of Detox

· Not as capable as Appium

· Has a smaller community

Cypress

Cypress is a testing tool which lets you write test faster and use it with no or less setup efforts. It is a secure and reliable way of testing applications which run on a browser. Cypress enjoys 11,453 stars on GitHub.

About Cypress

It is developer friendly:

Cypress is developed by keeping developers and QA engineers in mind. This helps them to work better.

It is open source:

Being an open source, it gets to enjoy the benefits coming from the community and this way the tools of Cypress is getting evolved faster and better.

It is built from scratch:

Cypress is developed on a new architecture completely, and it enjoys a lot more power. There is no Selenium.

What makes it better from others?

Real-time reloads:

Whenever changes are made in the tests, Cypress automatically reloads. You can see in your app in real time the commands getting executed.

Time travel:

While running tests Cypress takes snapshots. So to know what happened at every step you can simply visit the Command Log and hover over the commands.

Debug ability:

If your tests are failing continuously they debug from the familiar tools like Chrome Dev Tools directly. Debugging will take place at lightning speed by using stack traces and readable errors.

Automatic waiting:

Now you will not have to add sleep or waits into your tests. This task will be taken care of by Cypress as it automatically waits for assertions and commands before moving ahead. There will be no more async issues.

Enzyme

Enzyme is a JavaScript testing tool which is used for React to test the various React components and check the output. By knowing the output, you can also traverse, manipulate and simulate runtime.

It simulates React Components like jQuery and ReactDOM finding DOM. It can be used to check if components have certain props or have children and are also used to shallow render React components.

It enjoys 16,967 stars on GitHub.

React Native Tools

React Native Tools are nothing but an extension which offers a development environment for the projects builds on React Native. When you use this extension, you will be able to quickly run the react-native commands from the command palette after debugging the code. You can see details at

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.

A few reasons to choose Karma for your project are:

Test on real devices:

You can test the codes on real devices like phones or tablets or on real browsers.

Testing framework agnostic:

You can either write a simple adapter for any of the frameworks you choose or describe the tests using QUnit, Mocha and Jasmine.

Remote control:

Now you can control the complete workflow from your IDE or command line. All you need to do is just save the file, and Karma will run the tests.

Easy debugging:

Carrying out easy debugging via WebStorm or your IDE or Google Chrome.

Open source:

This testing tool is developed and maintained by the open source community which is present in GitHub.

Continuous integration:

It allows having simple integration with Travis, Jenkins or Semaphore.

It is released under the MIT license and it enjoys 10,629 stars on GitHub.

Mocha

Mocha is a JavaScript framework which is feature-rich and runs in the browser and on Node.js. This works on to make asynchronous testing fun and simple. Mocha tests run in a line which helps with accurate and flexible reporting. This helps with finding and mapping exceptions that are uncaught to the right test cases. It enjoys 17,623 stars on GitHub.

Some of the top features of Mocha are:

· Browser support

· Test coverage reporting

· Test retry support

· Extensible reporting

· Node debugger support

· JavaScript API for running test

Jasmine

Jasmine is a development framework which 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, etc. Additionally, it is very much influenced by Jspec, Rspec and JS Spec. It enjoys 14,298 stars on GitHub.

How to get started with Jasmine?

You can have Jasmine implemented in any development methodology. Here all you need to do is to visit the website https://jasmine.github.io/and then download the standalone library files for it from there. Once done that you can implement it in your application.

Some of the features of Jasmine are:

· It does not need to have DOM

· Behavior-driven development framework used to test JavaScript code

· It works on a platform which is JavaScript enabled

· Unit testing frameworks highly influence it

CALABASH

You can use Calabash to write and execute acceptance tests. It is used for mobile apps, and it is cross-platform supporting which means that you can use it for iOS and Android native apps. This testing tool is developed and maintained by Xamarin and is open source and free. Calabash comes with libraries which lets the test code to interact with native and hybrid apps programmatically. The interactions are about a number of different end-user actions. These end-user actions can be of:

· Assertions: This can be something like there should be a “Login” button

· Gestures: Gestures or touches for instance swipe, tap or rotate

· Screenshots: Take screendump of the current view you have on the screen of the current device.

You will find different automation libraries for Android and iOS on GitHub. The iOS version enjoys more than 18,000 stars while the Android version enjoys more than 16,000 stars on GitHub.

Appium

Appium is an open source tool which 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.

Appium mobile automation has been set around a philosophy which consists of four points and they are:

· In order to automate your app, you should not have to recompile or modify it.

· In order to write and run tests, you should not be limited to a specific framework or language.

· When it comes to automation APIs, the mobile automation framework should not repeat things from scratch.

· The mobile automation framework should be open source in all terms.

Conclusion

Here in this post, we have faced the different challenges which we face when carrying out React Native app testing. You can follow our blog article Top 10 React Native Developer Tools to Develop Powerful Mobile App in 2019. We have also discussed about the different types of testing for better clarity. The test automation framework used here are the most popular ones which are used to take care of native apps, the mobile web, hybrid apps and React Native apps. So whether you are a React Native developer or an app owner having an idea about such tools can be good.