Gain insights into Jest, a versatile testing framework. Learn about fundamental and advanced testing techniques, from unit tests to CI/CD integration, for comprehensive JavaScript application testing.

react.tar.gz

Run Tests

Run Tests - No Reset

Jest is a framework for testing applications developed in JavaScript. It has a well-documented and well-maintained range of tools to run tests in parallel. It is simple and works with projects using Babel, TypeScript, Node, React, Angular, Vue, etc. It works well for both client and server testing. 

This course covers Jest in-depth and is agnostic of any specific JavaScript framework. The course begins with the fundamentals of Jest testing, deconstructing the components of a test and covering how to compose basic unit tests and snapshot tests with Jest correctly. Next, it shows the testing of asynchronous code and the code that relies on external dependencies. Lastly, this course illustrates how Jest testing can effectively integrate into the real-world software development cycle through CI/CD pipeline.

It gives you hands-on experience in setting up Jest, types of testing, testing coverage, mocking, and native tooling depth.

…. To come 

… to come 

Mastering Jest: A Complete Guide to Testing

Now that we have an understanding of the Jest setup, we can learn how to write a test.

## In layman's terms

Simply put, a test does exactly one thing. A test tells us whether `Y` is true if we’re given `X`. `X` can be an argument passed to a function, an API response, a state, or a sequence of user behaviors, while `Y` can be a return value, the calling of a function, presence in the DOM, an error, etc.

Another way of saying this is that if `X`, we can expect `Y`. For example, let’s say we have the function below:

```
const addNumbers = (a, b) => {
  return a + b;
}
```
We would reasonably expect that if `3` and `4` are passed in, we will get a returned value of `7`. We can test this assumption like this:
```
expect(addNumbers(3,4)).toEqual(7);
```

Just like that, we have our first test.

## The structure


Now that we have an understanding of the Jest setup, we can learn how to write a test.

# In layman's terms

Simply put, a test does exactly one thing. A test tells us whether `Y` is true if we’re given `X`. `X` can be an argument passed to a function, an API response, a state, or a sequence of user behaviors, while `Y` can be a return value, the calling of a function, presence in the DOM, an error, etc.

Another way of saying this is that if `X`, we can expect `Y`. For example, let’s say we have the function below:

```
const addNumbers = (a, b) => {
  return a + b;
}
```
We would reasonably expect that if `3` and `4` are passed in, we will get a returned value of `7`. We can test this assumption like this:
```
expect(addNumbers(3,4)).toEqual(7);
```

Just like that, we have our first test.

# The structure


Learn how to properly compose a Jest test.

Introduction

Setting Up Jest

Jest Matchers

Writing Unit Tests

Writing Snapshot Tests

Asynchronous Code

Mocking

Mocking External Libraries

Working with Jest Mocks

Setup & Teardown

Test Coverage & CI/CD Pipelines

Test Coverage in Jest

Conclusion

Bonus: Best Practices

Bonus: Resources for Continued Learning

Appendix

The Composition of a Test

In layman’s terms