Node, Mocha: Simple factorial test suite with Mocha and Node assertion methods.

factorial.js

const Calculate = {
  factorial(number) {
    if(number === 0) {
      return 1;
    }
    for(let i = number - 1; i >= 1; i--) {
      number *= i;
    }
    return number;
  }
}

module.exports = Calculate;

factorial_test.js

var assert = require("assert");
var Calculate =  require('../factorial.js')

describe('Calculate', () => {
  describe('.factorial', () => {
    it('test factorial 5! is 120', () => {
      // Setup
      const expected = 120;
      const number = 5;
      // Exercise
      const actual = Calculate.factorial(number);
      // Verify
      assert.equal(actual, expected);
    });
    
    it('test factorial 3! is 6', () => {
      // Setup
      const expected = 6;
      const number = 3;
      // Exercise
      const actual = Calculate.factorial(number);
      // Verify
      assert.equal(actual, expected);
    });
    
    it('return 1 when 0!', () => {
      // Setup
      const expected = 1;
      const number = 0;
      // Exercise
      const actual = Calculate.factorial(number);
      // Verify
      assert.equal(actual, expected);
    });
    
  });
});