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Asynchronous Pair Programming Activity: Test-Driven Development (TDD) with Jest

Introduction

In this activity, you will be practicing Test-Driven Development (TDD) using Jest, an automated unit testing tool for JavaScript. The goal is to collaboratively solve a coding problem in pairs, following the RED-GREEN-REFACTOR cycle.

Prerequisites

  1. Ensure that you have Node.js and npm installed on your machine.

Activity Steps

1. Initial Setup

  1. Repository Setup:

    • Clone the provided files in Canvas > Files (unit-test, unit-mvc)
    • Navigate to the project directory: cd project-directory
    • You may decide to work on a version control platform (such as Github) to navigate around the changes. If not, you can always pass files around at the very least (very bad practice though :/).

  2. Install Dependencies:

    • Install Jest globally: npm install -g jest
    • Install project dependencies: npm install

2. Collaborative TDD

Pair 1: Developer A

  1. Write the Failing Test (RED):

    • Open the test file: (Write one if not yet present).
    • Write a test case for a specific functionality that is currently not implemented.
    • Ensure the test fails by running: npm test

  2. Switch Roles:

    • Commit the failing test changes: git commit -am "Add failing test for Module A"
    • Push the changes to the repository: git push origin main
    • Notify your partner (Developer B) to pull the latest changes.

Pair 2: Developer B

  1. Write Code to Make the Test Pass (GREEN):

    • Open the source code test file.
    • Write the minimum code necessary to make the failing test pass.
    • Run the tests: npm test
    • Ensure the test passes.

  2. Refactor Code (REFACTOR):

    • If necessary, refactor the code.
    • Ensure the tests still pass: npm test

  3. Write the Next Test Case (RED):

    • Open the test file again.
    • Write a new test case for the next functionality.
    • Ensure the test fails by running: npm test

  4. Switch Roles:

    • Commit the changes: git commit -am "Add failing test for next Module A functionality"
    • Push the changes to the repository: git push origin main
    • Notify your partner (Developer A) to pull the latest changes.

3. Iterative TDD

Continue the RED-GREEN-REFACTOR cycle, switching roles after each step, until the entire problem is solved. Remember to follow the TDD principles: write failing tests first, make them pass, and refactor as needed.

4. Submission

  1. Code Review:

    • Review the final code together.
    • Ensure all tests are passing.
    • Discuss any notable design decisions or challenges.

  2. Deliverables:

    • Each developer should push their final changes to the repository.
    • Submit the following in Canvas
      • The GitHub repository link.
      • The final version of the files: src/moduleA.js and src/__tests__/moduleATest.spec.js.
      • A file history of terminal commands:
        • Create a history file: history > history.txt
        • Commit and push the history file: git add history.txt && git commit -m "Add terminal command history" && git push origin main

Jest Installation and Usage

Jest Installation

  • Install Jest globally: npm install -g jest

Project Structure

  • Place your source code in the src/ directory.
  • Create a corresponding __tests__ directory inside src/ for your test files.
project-directory/
|-- src/
|   |-- moduleA.js
|   |-- __tests__/
|       |-- moduleATest.spec.js
|-- node_modules/
|-- package.json
|-- ...

Running Tests

  • Run all tests: npm test
  • Run tests for a sample (you can change this) specific file: jest src/__tests__/moduleATest.spec.js
  • Run tests in watch mode: jest --watch

Relevant Files

You may check out the following compressed files found in Canvas > Files

  • node-unit-test.zip
  • node-unit-mvc.zip