Скачать или смотреть Testing the ButtonComponent in React with Jest

Learn how to effectively test a button component in React using Jest and the React Testing Library, ensuring proper functionality with prop management.
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This video is based on the question https://stackoverflow.com/q/62873376/ asked by the user 'Jereme' ( https://stackoverflow.com/u/10591618/ ) and on the answer https://stackoverflow.com/a/62892716/ provided by the user 'Jereme' ( https://stackoverflow.com/u/10591618/ ) at 'Stack Overflow' website. Thanks to these great users and Stackexchange community for their contributions.

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Testing the ButtonComponent in React with Jest: A Step-by-Step Guide

When developing a React application, unit testing plays a crucial role in ensuring that your components are behaving as expected. One of the common challenges developers face is verifying that props are correctly passed and rendered within a component. In this post, we'll tackle a specific scenario: testing a simple ButtonComponent that accepts an optional iconName prop and ensuring this prop renders correctly. Let’s dive in!

The Problem Statement

You have a ButtonComponent that you want to test. This component takes in a label and an optional iconName prop. The goal is to verify two aspects:

The button renders correctly whether or not the iconName is provided.

If the iconName is passed in, the corresponding icon should be present in the document.

Here’s the initial implementation of your ButtonComponent:

[[See Video to Reveal this Text or Code Snippet]]

You’ve written a test case, but it doesn't pass due to an error stating: received value must be an HTMLElement or an SVGElement. Received has value: null. Let’s see how we can fix this issue.

Identifying the Issue

The problem lies in how you're handling the props within your test. Specifically, you were working with a shallow copy of the testProps object instead of modifying it directly. Additionally, the Icon component prepends a .fa class to the class name which needs to be accounted for in your assertions.

Step-by-Step Solution

1. Correctly Updating Props

To properly update the iconName in your test case, ensure that you modify testProps correctly. Here’s the updated approach you should follow:

[[See Video to Reveal this Text or Code Snippet]]

2. Modifying the Icon Prop Correctly

Modify the iconName directly in your existing testProps object:

[[See Video to Reveal this Text or Code Snippet]]

This line effectively updates the iconName property without creating a new object reference.

3. Rerendering the Component

After updating the props, rerender the ButtonComponent with the updated properties:

[[See Video to Reveal this Text or Code Snippet]]

4. Writing the Expectation

When checking if the icon is present, ensure to include the .fa prefix that the Icon component applies to the class name:

[[See Video to Reveal this Text or Code Snippet]]

Final Code Example

Here’s what the complete, corrected test case looks like:

[[See Video to Reveal this Text or Code Snippet]]

Conclusion

By correctly managing your props and ensuring that class names align with how React components render them, you can effectively test your components using Jest and the React Testing Library. This not only helps in catching bugs early in the development lifecycle but also contributes to building a reliable codebase. Happy testing!