text: 'use strict';
  
  var Formula = require('../index').Formula;
  var chai = require('chai');
  var expect = chai.expect;
  
  
  describe('Formula', function () {
  	// instance f to testing
  	var f;
  
      beforeEach(function () {
          f = new Formula();
      });
  
  	describe('#sum', function () {
          it('should sum two numbers together', function () {
              var result = f.SUM(2, 3);
              if (result !== 5) {
                  throw new Error('Expected 2 + 3 = 5 but was ' + result);
              }
          });
      });
  });