What is this?
A quick course for intermediate level developers looking to get started with testing using Jest and TypeScript.
We move fast, break things, then write tests to make sure they don't break again. The technologies used are:
Who is this for?
Highly motivated beginner who likes to jump in the deep end.
The Node.js section assumes basic Node.js/Express knowledge, and the React section assumes some React knowledge. The testing concepts are largely unrelated to those specific frameworks, so as long as you have some programming experience, you should be fine.
Get everything setup and starting writing some tests with Jest.
1.2 Your First Test
1.3 Adding an Assertion
1.4 Describing and Grouping Tests
1.5 Feedback Loop with Watch Mode
1.6 It.each for Concise Tests
2.0 Project: String Calculator
Put the skills learned in section one into practice by completing the String Calculator Kata.
3.0 Matcher Madness
Do a deep dive into the various matchers Jest provides, from toBe and toEqual to the more exotic resolves and rejects matchers.
3.2 toEqual, not
3.4 Resolves matcher for Promises
3.5 Rejects matcher for Errors
3.6 toHaveBeenCalled and Mock Functions
3.7 Waiting with the Done Callback
4.0 TypeScript, Node.js and Jest
We introduce TypeScript and Jest by developing and testing a Node.js API. Note: This section assumes basic knowledge of Node.js and Express.
4.1 TypeScript and Jest with ts-jest
4.2 Express Setup
4.3 The Jest Lifecylce: Before and After Hooks
4.4 Better Types
4.5 Adding JWT and a Refactor
4.6 Authorization Header
4.7 Testing for Success
4.8 Testing for Failure
4.9 Alternative Failed Assertion Syntax
5.0 TypeScript, React and Testing in a DOM Environment
Build a toy React app and see how to use TypeScript and Jest for DOM based testing with Testing Library. Note: this section assumes basisc knowledge of React.
5.1 Create React App and TypeScript
5.2 Rendering with Testing Library
5.3 Testing Library Assertions - getByText
5.4 useState and Asynchronous Assertions
5.5 Fetchign Data with useEffect
5.6 More Async Behavior with findAll
5.7 Mocking Axios with Jest Mocks
5.8 Toggling Todos
6.0 Jest Tips and Tricks
Learn some of Jest's more advanced features. Write your own custom matchers with TypeScript and write more robust, reuseable and (mostly) type-safe mocks.
6.1 Section Overview
6.2 Custom Matcher API
6.3 Implementing the Matcher
6.4 Typing the Matcher
6.5 Setting up for Module Mocking
6.6 Inline Mocks Review
6.7 The Problem with Inline Mocks
6.8 Manual Mocks
6.9 Default Module Data
6.10 Typing the Mock Module
6.11 Improving the Spec Types
6.12 Jest Spies
6.13 What Next? More Learning Resources
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