Learn the smart, efficient way to test any JavaScript application.

Do you know what a testing framework does? Do you know what makes a testing framework different from a testing or assertion library? The best way to use a tool effectively is to understand how it works. And the best way to understand how a tool works is by making it yourself!

In this short course, we’ll learn how testing frameworks and assertion libraries work by building our own, simple version of each.

When running unit tests, you don’t want to actually make network requests or charge real credit cards. That could… get expensive… and also very, very slow. So instead of running your code exactly as it would run in production, you can modify how some of your JavaScript modules and functions work during tests to avoid test unreliability (flakiness) and improve the speed of your tests. This kind of modification can come in the form of stubs, mocks, or generally: “test doubles.”

There are some great libraries and abstractions for mocking your JavaScript modules during tests. The Jest testing framework has great mocking capabilities built-in for functions as well as entire modules. To really understand how things are working though, let’s implement some of these features ourselves.

There are a ton of ways your application can break. One of the most common sources of bugs is related to typos and incorrect types. Passing a string to a function that expects a number, or falling prey to a common typo in a logical statement are silly mistakes that should never be made, but this happens all the time.

We could write a comprehensive suite of automated tests for our entire codebase to make certain mistakes like this never happen, but that would likely be too much work and slow development down to be worth the benefit. Luckily for us, there are tools like ESLint, TypeScript, Prettier, and more which we can use to satisfy a whole category of testing with a great developer experience.

The person using your application components shouldn’t have to know or care what framework(s) you used to write your application. Guess what: Neither should your tests.

This course explores the dom-testing-library using 11 different frameworks, from React to Svelte. You’ll get hands-on experience writing tests for any JavaScript framework, giving you the confidence you need to ship your JavaScript application with your framework of choice.

Jest is a fully featured testing framework with a developer experience that is second to none. It’s remarkably simple and flexible at the same time. For simple use cases, you often don’t need to configure anything, install and enjoy the built-in coverage and watch mode support.

In a real-world application though, you’ll often have needs specific to your application, especially when testing browser-based applications. You'll need to handle Webpack loaders, dynamic imports, and custom module resolution which Node.js does not support.

In this course we’ll go over ways you can optimize your Jest configuration to make testing real-world JavaScript applications a delight. We’ll cover what’s already been mentioned in addition to Babel support, code coverage, how to make watch mode even more helpful, and how to run test suites with entirely different configurations.

If you want to ship your applications with confidence - and of course you do - you need an excellent suite of automated tests to make absolutely sure that when changes reach your users, nothing gets broken. To get this confidence, your tests need to realistically mimic how users actually use your React components. Otherwise, tests could pass when the application is broken in the real world.

In this course, we’ll write a series of render methods and run a range of tests to see how we can get the confidence we’re looking for, without giving up maintainability or test run-speed.

Cypress is an incredibly powerful web testing tool. It’s capable of testing any web application. Its architecture places it a cut above similar end-to-end testing tools. Its developer experience is best-in-class. And because Cypress runs your tests in the same context as the rest of your application, you’re able to get speed, reliability, and debuggability that are just a long - distant dream with similar tools. The catch? There is no catch. Cypress is exceptional.

In this course, we’ll go over how you can install, configure, and script Cypress to test modern, real - world JavaScript web applications.

Backends hold so much of our application's business logic that is often used to support multiple clients (web, mobile, and other native platforms). This logic is critical to get right and deploying a breaking change to this can be devastating to your company's goals (not to mention the bottom-line). Increasing your "deployment confidence" is crucial and automated testing is the best way to do that.

As Node.js continues to grow in usage around the world, learning how to test this mission-critical code in a way that increases developer velocity as well as confidence becomes increasingly important. In this workshop we use an Express.js example and focus on the patterns and practices that you need to learn so you can apply what you learn to test your code written in any Node.js web framework.

You'll learn:

• Testing Pure Functions
• Testing Middleware
• Testing Controllers
• Testing API routes
• Mocking third party dependencies
• Testing authenticated code