Lesson Weekend

Many of our computer science lessons involve building small logic-based applications to try out new concepts. These applications will not have a UI. Instead, we will use a test-driven environment with JavaScript to build out these applications.

We'll use a very basic setup for testing. We recommend creating a repo that uses the basic structure below. Then you can reuse the files in the repo for any computer science lessons that use TDD. This basic testing setup is also very useful for when you want to write, experiment with, and test code on your own.

Each TDD project will have the following structure:


We do not need webpack - we just need enough of an environment to write and run tests.

Here's the package.json file:

  "name": "name-of-project-here",
  "version": "1.0.0",
  "description": "Description of project",
  "scripts": {
    "test": "jest --coverage"
  "devDependencies": {
    "@babel/core": "^7.6.4",
    "@babel/plugin-transform-modules-commonjs": "^7.6.0",
    "jest": "^24.9.0"

As we can see, it's very pared down - all we need is Jest and Babel. A quick reminder: Babel is necessary for Jest to recognize ES6 import and export statements. Since we only need to test our code and there's no need for a web implementation, we don't need a module bundler like webpack. Obviously, you'll want to update the "name" and "description" of the project as needed.

Don't forget to run npm install after adding package.json.

Here's the .babelrc file:

  "env": {
    "test": {
      "plugins": ["@babel/plugin-transform-modules-commonjs"]

You should also include the Jest debugging tool as described in this lesson. If it's already installed on your machine, you just need to add a .vscode file with the following configuration:

  // Use IntelliSense to learn about possible attributes.
  // Hover to view descriptions of existing attributes.
  // For more information, visit: https://go.microsoft.com/fwlink/?linkid=830387
  "version": "0.2.0",
  "configurations": [
      "type": "node",
      "name": "vscode-jest-tests",
      "request": "launch",
      "program": "${workspaceFolder}/node_modules/jest/bin/jest",
      "args": [
      "cwd": "${workspaceFolder}",
      "console": "integratedTerminal",
      "internalConsoleOptions": "neverOpen",
      "disableOptimisticBPs": true

Note: Sometimes students will have issues with tests fully passing using the Jest debugging tool or when running tests in VS Code. If that ever occurs, please run the tests in the terminal as well with $ npm run test.

This is all we need to get started!

Lesson 3 of 11
Last updated more than 3 months ago.