Gain insights into writing automated tests for React apps with Jest and React Testing Library. Learn about simulating user interactions and testing asynchronous parts to enhance app reliability.

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Jest - lesson 2

Jest with run command

Jest verbose

Jest coverage

Jest snapshot update

Jest react

Jest react-npm start

Jest react-copy

Jest react-C4

Jest react-C6

Jest react start c6

Jest - lesson 2-copy

Jest sandbox

Jest coverage-copy

Jest react-C4-start

Jest react-C4-start-5000

Jest react-npm start-5000

Jest react start c6-5000

Jest react-C8

The skills acquired from this course will allow you to write automated tests on your React app using Jest and React Testing Library, which are the de-facto testing tools for React. These tests will allow you to ship new versions of your app with confidence. The tests will also allow you to increase your release frequency, allowing you to get features to your customers quicker.

You will learn how to write robust tests that are resilient to breaking when code is improved and refactored, reducing maintenance costs.
The course will teach you how to simulate a user interacting with the app. Beyond that, it will also teach you how to robustly test asynchronous parts of the app.

Regular quizzes and exercises will reinforce knowledge throughout the course.

Testing React Apps with Jest and React Testing Library

# Starter project

The project for this lesson contains a `Message` component that displays either an error or success message.

A copy of the project is in the code widget below. Click the **“Run”** button to run the app:

module.exports = {
  presets: [
    ["@babel/preset-env", { targets: { node: "current" } }],
    ["@babel/preset-react", { runtime: "automatic" }],
  ],
};


React

Dart

GoJS React

Typescript React

Vue.js

Run the app.

We will see that an error message and success message consists of an image followed by some text.

The project contains a half-implemented test to verify the correct image is rendered for an error message. We will fully implement this test in this lesson.

The code widget below contains a copy of the project and runs the tests when the **"Run"** button is clicked:

# The `ByAltText` query type

To finish the test implementation, we need to check that the correct `img` element is within the DOM.

There is a query type called [`ByAltText`](https://testing-library.com/docs/queries/byalttext), which gets an `img` element with a particular `alt` attribute.

There is a query type called `ByAltText`, which retrieves an `img` element with a particular `alt` attribute.

>**Note:** that the value of the `alt` attribute is output if the image isn’t found. A screen reader will read out the `alt` attribute as well. Images with `alt` attributes make the app better.

If we call the `ByAltText` query with the text `"cross"`, it should find the *cross* image.

What variant of `ByAltText` should we use to select the image? Why?

Learn more query types for selecting elements in this lesson.

Introduction

Getting Started with Jest

Using Matchers

Getting Started with React Testing Library

React Testing Library Queries

Firing Events

Mocking

Testing Different Types of Components

Appendix

Querying Images

Starter project

The `ByAltText` query type

Querying Images

Starter project

The ByAltText query type

The `ByAltText` query type