flexpath-unit-testing-with-jest-exercises

Exercise overview

These exercises will let you practice writing Unit Tests for a pre-built application: bookManager.js

Getting Started

1. Using Visual Studio Code, open the folder flexpath-unit-testing-with-jest-exercises wherever you saved it on your device.

2. Then open the flexpath-unit-testing-with-jest-exercises/exercise folder. Inside this folder are the following files:

   • bookManager.js - a pre-built application that you will be writing tests for
   • package.json - manages packages and scripts for the bookManager app
   • jest.config.js - configuration file that tells Jest how to behave in this folder
   • EXERCISE-INSTRUCTIONS.txt - the instructions for each exercise
   • tests/bookManager.test.js - the starting file where you will write your tests.

3. Before you start these exercises, open your VS code terminal, navigate inside of the exercise/ folder, and run npm install in the terminal. This will install all npm packages required for you to complete these exercises.

4. As you work through the exercises outlined in EXERCISE-INSTRUCTIONS.txt, you will create tests based on the exercise prompt. Each time you create a test, you should run it to ensure your test is behaving as expected.

   There are also some questions that don't require code for an answer. In those cases, save your answers for these questions directly inside of the EXERCISE-INSTRUCTIONS.txt file.

5. You will run your tests by opening your VS Code terminal, navigating inside of the exercise/ folder using the change directory cd command, and you will run the following command: npm run test.

6. Once you get to exercise 9, feel free to create new [exercise_xx].test.js files inside of the /exercise/tests/ folder to organize your code.

   As long as your file name ends with .test.js and its in the tests/ folder, Jest will be able to find it and run it when you run npm run test in your VS code terminal.

The solutions for these exercises are in their own Github repo. The link to the GitHub repo is inside of /solutions/exercise-solutions/solution-repo.txt.

Make sure to fork the solution repo, THEN clone it to your local device to run the code.

We have also provided a video jest-exercises.mp4 showing you how to run npm install in the proper locationand run Jest on your .test.js files.

VIDEO DISCLAIMER - You will need to clone the repo to your local device before you can watch the .mp4 file since GitHub does not support watching it from here.

 

Summary of JavaScript Concepts Covered in These Exercises

Exercises instructions are in the EXERCISE-INSTRUCTIONS.txt file

You will be writing your tests inside of /exercise/tests/bookManager.test.js

For some of the exercises, feel free to create a new file inside of the tests folder to hold its test code.

You can name the new file anything you want, just make sure it is in the tests folder and the file name follows this format: [filename].test.js

Steps to run your tests:

1. Make sure you are inside of the exercise folder inside of this repo in your VS Code terminal

2. Once you are inside the exercise folder, you can run your tests by running the command npm run test

3. Unit Testing Fundamentals:

   • The purpose of unit tests and how they fit into the software development lifecycle.
   • Differences between manual testing and automated unit testing.
   • Test-driven development (TDD) and the benefits of writing unit tests first.

4. Jest Basics:

   • Installing Jest and setting it up for a project using npm.
   • Writing simple unit tests using Jest's test and expect functions.
   • Understanding matchers and how to use them for various types of assertions.
   • Running Jest tests using the command line and configuring Jest with a configuration file.

5. Test File Organization:

   • Structuring test files using describe blocks to group related tests.
   • Using hooks (beforeAll, afterAll, beforeEach, afterEach) to perform setup and teardown tasks.

6. Common Matchers in Jest:

   • Using matchers like toBe, toEqual, toStrictEqual, toContain, toMatch, toBeTruthy, toBeFalsy, and toThrow.
   • Differences between strict and loose equality checks in Jest.

7. Mocking and Spying:

   • Creating mock functions to isolate tests and avoid dependencies on external services.
   • Using Jest's automock feature to automatically mock modules.
   • Writing manual mocks to customize the behavior of mocked functions.
   • Using spies to monitor calls to functions and assert they were called correctly.

8. Testing Asynchronous Code:

   • Writing tests for asynchronous functions using Promises, async/await, and callbacks.
   • Using Jest's resolves and rejects for testing promise-based code.
   • Ensuring tests wait for asynchronous code to complete using Jest's done callback.

9. Code Coverage:

   • Measuring code coverage and understanding metrics like statement, branch, function, and line coverage.
   • Collecting coverage statistics using Jest and configuring thresholds to enforce code quality.