Stories:

1. As a user, I'd like a simple API so that I can do addition.
2. As a user, I'd like a simple API so that I can do subtraction.
3. As a user, I'd like a simple API so that I can do multiplication.
4. As a user, I'd like a simple API so that I can do division.

Steps (from scratch):

Setup

1. Create project directory: `mkdir calc && cd calc`
2. Create package.json: `npm init`
3. Install Babel: `npm i babel-cli babel-presets-env --save-dev`
4. Configure Babel in package.json:

"babel": {"presets": [["env",{"shippedProposals": true}]]}

Unit Tests

1. Install unit testing dependencies: `npm i mocha chai babel-register --save-dev`
2. Add `test:unit` scripts to package.json

"test:unit": "mocha *.test.js --require babel-register",

3. Add empty calc.js
4. Add test file, calc.test.js, and write test for add API
5. Run `npm run test:unit`. tests should fail
6. Write and export add function in calc.js
7. Run `npm run test:unit`. tests should pass.
8. Repeat 4-7 for subtract, mulitply, and divide functions

Unit Test Coverage

1. Add test coverage reporting: `npm i nyc --save-dev`
2. Change `test:unit` to call instanbul (nyc):

"test:unit": "nyc mocha *.test.js --require babel-register"

Linting

1. Add Standard and Babel-ESLint support: `npm i standard babel-eslint --save-dev`
2. Configure Standard in package.json

"standard": {
    "parser": "babel-eslint",
    "env": {
    "node": true,
    "mocha": true
    }
}

3. Add `lint` script to package.json

"lint": "standard *.js --fix"

4. Run `npm run lint`, and fix any issues

Behavioral Testing

1. Install Cucumber JS: `npm i cucumber --save-dev`
2. Add `test:bdd` script to package.json

"test:bdd": "cucumber-js --require-module babel-register",

3. Create features directory: `mkdir features && cd features`
4. Create feature file for add feature, `add.feature`
5. Run `npm run test:bdd`, which will output stubbed tests
6. Create step file and implement tests, `add.steps.js`
7. Run tests: `npm run test:bdd`
8. Repeat for subtract feature

Implement REST API

1. Install Express: `npm i express --save`
2. Create index.js
3. Add routes for our API functions
4. Add `start` script to package.json

"start": "babel-node index.js",

4. Start server, `npm start`

Automation Tests

1. Install Selenium Webdriver and Babel Polyfill: `npm i selenium-webdriver babel-polyfill --save-dev`
2. Create automation test directory: `mkdir automation && cd automation`
2. Add `test:auto` script to package.json

"test:auto": "mocha automation/*.auto.js --require babel-register",

4. Create test, `api.auto.js`, and implement tests.