Test Adequacy Activity

Introduction

We define a simple REST web server using Express and Typescript. The server connects to a MongoDB database and interacts with it thru an object data modeling library Mongoose. Unit tests are written in jest to verify the behavior of the REST endpoints. Stryker, a mutation testing tool, is used to measure test adequacy.

Setup

Before proceeding, you will need to install the following:

• Node.js (vs20 or later). Download here
• npm package manager. Comes bundled with Node.js

Verify that installation was successful by running the following commands from a terminal:

node --version
npm --version

Both commands should print a version number (e.g., v24.3.0)

Once you have setup the required software. Setup the dependencies for this project by running the following command. For all subsequent commands we will assume you are in the current directory.

npm install

If for some reason the above command fails then do the following:

• Delete node_modules directory if any
• Delete package-lock.json file
• Run the npm install command again

Useful Project Commands

The following commands have been configured in package.json. You can run them from a terminal.

Command	Purpose
npm run dev	Starts the server using ts-node (no build step necessary)
npm run build	Compile TypeScript to dist/
npm start	Run compiled output (Build step necessary)
npm test	Run all Jest tests
npm run test -- /path/to/test/file	Run a specific test file
npm run test:coverage	Jest with coverage report
npm run stryker	Run Stryker mutation testing

Project Structure

src/
├── models/         # Mongoose Schemas
├── routes/         # REST endpoints
├── app.ts          # Express route definitions and middlewares
├── index.ts        # Server entry point (not tested directly)
└── __tests__/      # Jest tests

Stryker Thresholds

The following table defines sample threshold values for mutation test scores. These vary depending on the project and what you deem as core application logic that needs to be tested thorougly. Adjust them in stryker.config.mjs accordingly.

Level	Score
High (green)	≥ 80%
Low (yellow)	≥ 60%
Break (fail CI)	< 50%

Running the run stryker command will generate a report in reports/mutation/mutation.html.

For You To Do

Do the activity in activity.md