Learn React Testing: Course OverviewCourse Overview

Jest

Begin testing quickly with Jest.

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Key Concepts

Review core concepts you need to learn to master this subject

What is Jest?

Installing Jest

Configuring Jest

The test() function

Detecting false positives

Testing async code: callbacks

Testing async code: Promises

Mocking functions with jest.fn()

What is Jest?

Jest is a testing framework for JavaScript that includes both a test-runner and assertion functions in one package.

Unit Testing with Jest

Lesson 1 of 1

1
What is Jest?
As developers, we strive to make our code bulletproof from bugs that could break our applications. One process that can help us get closer to “unbreakable code” is testing while _testing framewor…
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2
Installing Jest
Before we can begin testing our code with Jest, the jest package must first be installed and configured. We will download Jest via the Node Package Manager (NPM) by running the followin…
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3
Configuring Jest
Before we move on to actually writing our tests, we should cover a few best practices. By default, each test produces the terminal output that we saw in the previous exercise. Jest allows us to c…
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4
Unit Testing with Jest (Part 1)
Now that Jest is installed and configured it is time to set up our first unit test. A unit test is designed to test the smallest unit of your code, like a single function. Let’s consider testing …
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5
Unit Testing with Jest (Part 2)
With our test() container set up, it is time to finish our first unit test by writing assertions to validate the various features of our code. To do this, Jest provides the expect() function. T…
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6
Matcher Functions
Congrats on writing your first unit test! In the last exercise, you used the expect() assertion function along with the .toEqual() matcher method. Let’s learn about a few more common matcher method…
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7
Testing Async Code with Jest (Part 1)
Armed with how to write simple unit tests, we will now add a layer of complexity by exploring how to test asynchronous code in Jest. Let’s return to the findRecipes() function from the recipes mo…
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8
Testing Async Code with Jest (Part 2)
We will now explore testing functions that return a Promise. Let’s return to the findRecipe() function altere…
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9
Mocking with Jest (Part 1)
Over the past few exercises, we have been analyzing the findRecipe() function which makes an REST API call to fetch the recipe data. Testing with a real REST API is not ideal for a few reasons: * …
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10
Mocking with Jest (Part 2)
Now that we have a module set up with our mocked function it’s time to use it within our Jest test for findRecipe(). Remember, we want to replace the actual apiRequest() function with the mocked on…
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11
Let's Review!
Great work! We have covered a lot over this lesson. Let’s take a moment to review: * We have learned that Jest is an easy-to-use framework for testing in a JavaScript environment because it combine…
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