JavaScript JavaScript Unit Testing Improving Our Tests Catching an Error

Christopher Lebbano
Christopher Lebbano
15,337 Points

Test spec, not sure why this isn't working

Not too sure why this isn't passing. Any ideas?

subtraction_spec.js
var expect = require('chai').expect;

describe('subtraction', function () {
  var subtraction = require('../subtraction.js');
  it('only works with numbers', function () {
    var one = 'one';
    var two = 'two';
    expect(subtraction(one, two)).to.throw(Error, 'subtraction only works with numbers!');
  });
});
subtraction.js
function subtraction (number1, number2) {
  if (typeof number1 !== 'number' || typeof number2 !== 'number') {
    throw Error('subtraction only works with numbers!');
  }
  return number1 - number2
}

1 Answer

Hi Christopher,

You have to pass a function reference into expect() so what you can do is wrap your subtraction function call with an anonymous function.

expect(function() {subtraction(one, two)})