To install and run Mocha, the Node.js testing module, we install the mocha package globally.
To install it, we run
npm install --global mocha
to install mocha globally.
We can also install it in the project folder as a dev dependency with
npm install --save-dev mocha
Then in package.json, we add
{
  //...
  "scripts": {
    "test": "mocha"
  }
  //...
}
to add the test script to run mocha installed in the node_modules folder.
