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JavaScript JavaScript Unit Testing Improving Our Tests Catching an Error

Posted by Deloris Luckett
Deloris Luckett
6,418 Points

The subtraction function in subtraction.js throws an error if it's called with anything other than numbers. Write a spec

var expect = require('chai').expect

describe('subtraction', function () { var subtraction = require('../WHEREVER')
it('only works with numbers', function () { // YOUR CODE HERE expect(function () { subraction() }).to.throw('subtraction only works with numbers !'); }) })

above is subtraction spec js

below is subtraction js function subtraction (number1, number2) { throw error('subtraction only works with numbers!') if (typeof number1 !== 'number' || typeof number2 !== 'number') { throw Error('subtraction only works with numbers!') } return number1 - number2 }

does anyone know why im not passing

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

describe('subtraction', function () {
  var subtraction = require('../WHEREVER')  
  it('only works with numbers', function () {
    // YOUR CODE HERE
  })
})
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

Peter Lord
Peter Lord
10,034 Points
Peter Lord
Peter Lord
10,034 Points

I don't know much about Chai specifically, however, the chai documentation states to do expect(badFn).to.throw(). More information can be found here https://www.chaijs.com/api/bdd/#method_throw

Below is the correct code to pass the quiz. 

var expect = require('chai').expect

describe('subtraction', function () {
  var subtraction = require('../WHEREVER')  
  it('only works with numbers', function () {
    // YOUR CODE HERE
    expect(function () {
      subtraction()
    }).to.throw('subtraction only works with numbers!');
  })
})