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.

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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

# The callback pattern
A **callback** is a function that is passed as the last argument to another function and called at the end of that function. It looks something like this:

```
function logger(str) {
  console.log(str);
}

function getUserName(user, callback) {
  const { name } = user;

  callback(name);
}

getUserName(u, logger);
```

# Callbacks and Jest
We can use Jest to test functions that use callbacks to manage asynchronous code. To do this, we can create the callback in our test and then pass it to our asynchronous function. We just have to ensure that we are following best practices on how we compose these tests.

## The wrong way
It may be our instinct to just assert at the end of the callback, as depicted in the code below:



Learn how to use Jest to test asynchronous code with callbacks.

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

Testing with Callbacks

The callback pattern