tester.js

const {
  add, subtract, divide, multiply,
} = require('.');
assert = require('chai').assert;

describe('Sum', () => {
  context('Adding 1 and 1', () => {
    it('should return 2', () => {
      assert(add(1, 1) === 2);
    });
  });
});

describe('Subtract', () => {
  context('Subtracting 1 from 1', () => {
    it('should return 0', () => {
      assert(subtract(1, 1) === 0);
    });
  });
});