Testing is one of the essentials in software development. Without a good testing process, it's normal to break the parts that were not developed. Developers don't like testing other than unit testing of them. But manual browser testing is always boring. It's hard to track what has been tested.
End-to-end testing is pretty tough to automate for React testing, due to the lack of tools out there. That's why React developers sometimes have to go through manual testing.
This blog post will go through everything you need to know about running tests and testing react components. So hang in there and keep reading!
React testing is simply the process of ensuring that your React app would work as it should. But since React apps are made of components, testing can also be defined as the process of verifying the internal and external state of components and how they interact with each other.
If you're new to react apps, we recommend using create react app, which gives you a simple and easy way to get started with react.
If you're starting from scratch, we recommend using the react testing library, which is a library for testing react components.
Now back to the main topic.
There are four different React testing types you should follow: unit tests, component tests, end-to-end tests, and snapshot tests.
A unit test verifies that there's no bug in a small bit of code. These bits of code usually do not possess any React-specific behavior, but it's important to test them because a bug can affect the implementation details of the larger React component.
Unit tests are typically simple to write and deploy. The objective is to verify that the unit produces the expected result for a given input, and all you need is a framework-agnostic library such as Jest, Mocha, or Jasmine.
Component tests verify the behavior of a React component in isolation. The test is similar to integration testing as it focuses on the functionality exposed by the component. Examples of component tests include testing a click and text entry or testing how the component responds to a user action.
Component tests are usually executed using React libraries such as React Testing Library and Enzyme. When testing components, it's vital to render them as the tests were running in a web browser. This is one of the reasons why you have to use a React-specific library during component tests.
End-to-end tests are the most complex react testing type because they verify how components interact to form a user workflow. The test attempts to mimic user behavior on your application, but it's very hard to maintain because it is not easy to express user behavior in code.
Although componentization has numerous advantages, development teams need to be aware that a seemingly simple change in your app's common components can affect the entire application. Snapshot testing attempts to measure the extent to which a change within a component affects the entire application.
This category of test provides better coverage for unseen bugs when compared with component or unit tests. However, the tests typically come up with many notifications, the majority of which aren't bugs you should be concerned about.
React testing frameworks help you simplify your test scripts and determine how you want to test your applications. Below are some of the most broadly adopted frameworks you should consider using the next time you want to test your React application:
Jest is the recommended test framework within React's docs. So, it's no surprise that it's the most popular React testing framework around. The platform is maintained by Facebook, which also maintains React, and it can serve as a test DSL and test runner, just like Mocha. However, Jest boasts numerous additional features specific to React testing, and it's also useful for executing snapshot testing.
For example, Jest allows you to mock modules and timers, thus giving you greater control over how the code executes. Furthermore, Jest's default testing setup helps you skip manual configurations, an advantage you may not get with other frameworks.
The native React Testing Library possesses numerous functions that make testing your React apps easier. It's particularly useful for component testing because you don't have to include the implementation details of your components.
In the library, you will add a test block to the render method that will test if the landing page renders accurately.
The library's utilities help you mimic a real user while querying the DOM, thus giving you more confidence that your application's UI and UX will match the user specifications. It also promises a test base that's maintainable in the long term.
Enzyme fulfills virtually the same purpose as React Testing Library by making component testing easier and more maintainable. However, unlike React Testing Library, Enzyme focuses on the implementation details of your app's components.
Using Enzyme gives you access to the props, state, and children components while writing your test, and such information can, in turn, be used to run your assertions.
Traditional end-to-end testing frameworks like Selenium, Cypress, and Puppeteer have some limitations in testing React apps. Here is the list:
As you know React renders everything in the background in a Virtual DOM and then replaces the affected parts with the re-rendered virtual DOM. Traditional approaches like Selenium and Cypress may not be able to act on the elements that were on the page but now it's not. Because React has already replaced the DOM element when you hovered over it.
This is a super annoying exception in Selenium or Cypress or Puppeteer. It may not happen all the time but sometimes it might give you headaches.
Depending on selectors is not a good scenario most of the time. Because the design is not a constant variable. It might change when it does, it might break changes.
Furthermore, React or CSS Module is going to hash the classes if your project is set up that way. The hash will change each time you deploy.
The CSS module output will look like this -
Traditional end-to-end testing frameworks cannot check visual differences. This is pretty crucial when you want to make sure a graph is existed on the page or is loaded correctly.
If you've been looking for a testing platform that empowers you to execute effective end-to-end testing, PreFlight should be the first name on your mind. The platform employs a radically different approach from traditional testing frameworks, allowing you to test without experiencing any of the limitations mentioned above. Here are some of the advantages of adopting PreFlight for your React testing:
PreFlight is a fully web-based no-code testing platform. You do not have to download or install any software on your computer before using PreFlight. Rather, you create and execute tests by recording your actions in real time. Furthermore, the platform integrates seamlessly with most continuous integration/continuous delivery tools, and you can easily test their compatibility with your app.
PreFlight takes the difficulty out of creating automated tests. You can use PreFlight's recorder to capture all your interactions with your react app and have them reproduced automatically with PreFlight's test runner. The recorder is not affected by changes synced via the Virtual DOM. Thus, you can rest assured you won't have flaky tests.
One of the secret sauces PreFlight has is Context-Awareness. It is one of the amazing AI functionalities mentioned in the "Best AI in Automated Software Testing Tools". It can understand the page structure as humans. There is a selector change? No problem! There is a UI change? Again, no problem! 😁
If PreFlight cannot understand the page structure, it will scan the page and try to find the element with Computer Vision (CV) and Optical Character Recognition (OCR) and some object detection algorithms to find it.
Either way if PreFlight found the element with Context Awareness or CV, and the test was successful, it'll automatically update the selectors for the next run to run it faster next time.
When you use traditional end-to-end testing tools, you have no option but to look for compatible plugins that can handle visual testing. However, with PreFlight, your visual testing needs are well taken care of. What's more? PreFlight's built-in visual testing tool only detects visual regressions that are germane to your users' experience. As a result, you won't get notifications about bugs outside the scope of your test.
If you're struggling with React Testing, you're not alone. Even ardent software testers who are not conversant with React testing may need some time to master the process before they can confidently test React apps. Below are some of the most common questions about React testing and their answers.
A react test ascertains that your react application behaves as anticipated. Broadly speaking, the test verifies the internal behavior of a component (unit test), external behavior of a component (component test), and how one or more components interact with each other (end-to-end test).
It's virtually impossible to cover all test scenarios during React testing. Thus, you have to prioritize the components or functions that are most important to your application. Usually, these would include common helper functions, common components, and workflows that are vital to a positive user experience.
React testing is typically executed with testing libraries like Jest, React Testing Library, and Enzyme. These libraries will take care of most of your unit and component test cases and are easy to install and run (via npm install and npm test, respectively). On the other hand, end-to-end testing frameworks usually require coding, but you can still rely on a platform like PreFlight to get comprehensive coverage for your critical workflows without writing a single line of code.
The duration of a React test depends on the type of test and its complexity. While unit tests can be executed within milliseconds, end-to-end tests may take anything from a few to several minutes, depending on the complexity of the workflow you're testing.
React test automation takes the hard work out of testing while ensuring you detect and fix bugs that could affect the functionality or performance of your app. However, testers struggle to find an automated testing tool that covers most test cases with very little or no limitations.
If you're in those shoes, sign up to book a demo or create your first React test in under a few minutes!