Using external class during client side Mocha unit testing

Question

I am running unit tests on a javascript class using Mocha using the follow methodology, firstly the test:

var base = require('../moduleone.js');

describe("some test", function() {
    it("description", function() {
    var check = base.toBeTested(dummyValue)
    //test is here ...
    });
});

the moduleone.js containing function to be tested:

function toBeTested(category){
    //below I calling an assert function defined in moduletwo
    //works fine when running in browser
    assert(type(category)=='string','category is string type');
    //more code..
    return something

module.exports.toBeTested = toBeTested;

moduletwo.js:

function assert(outcome, description) {
    //see code.tutsplus.com quick and easy javascript testing with assert
    var li = outcome ? 'pass' : 'fail';
    if (li == 'fail') {
        console.log('FAIL: '+description);
    }
    else {
        console.log('PASS: '+description);
    }
}

The issue I have is mocha doesn't know anything about moduletwo and when the moduleone function calles the function in moduletwo mocha throws a ReferenceError: assert is not defined. How can I link all my dependencies so that mocha can see them?

thebearingedge · Accepted Answer · 2016-03-01 02:01:24Z

1

In your moduleone.js be sure that you are requireing moduletwo.js to bring your assert function into scope for moduleone.js. Otherwise, you get a ReferenceError, not for any reasons with mocha, but because moduleone does not have access to assert.

// moduletwo.js
function assert(outcome, description) { /* your functionality */ }

module.exports = assert


// moduleone.js
var assert = require('./moduletwo')

function toBeTested(category) { /* your functionality that uses assert */ }

module.exports.toBeTested = toBeTested

Now, with regards to that tutorial. If you are following it to learn how to make an easy assert module, that is fine. But if you are trying to test some code that does something else, consider using an existing assertion library like chai. For example:

// example.test.js
var expect = require('chai').expect
var isValidCategory = require('./is-valid-category')

describe('isValidCategory(category)', function () {

  it('validates string categories', function () {

    expect(isValidCategory('A String Category')).to.be.true

  })

  it('does not validate non-string categories', function () {

    expect(isValidCategory(['an', 'array', 'somehow'])).to.be.false

  })

})

// is-valid-category.js
module.exports = function isValidCategory(category) {

  return typeof category === 'string'
}

edited Mar 1, 2016 at 2:01

answered Feb 6, 2016 at 19:16

thebearingedge

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4 Comments

Don Smythe Over a year ago

for the case given when I exported one function from a module your solution works perfectly. However I require tens of functions from several files so I exported each function from moduletwo eg module.exports.assert = assert; module.exports.type = type; then added to module1 the code: var utils = require('./moduletwo.js') and called each function using: utils.assert(utils.type(category)...); The problem is my app is client side only so exposing functions through require won't work. Of course I could add everything to one big file but is there another way?

thebearingedge Over a year ago

Your requirement of having multiple properties on module.exports is ok. Check out browserify for bundling CommonJS modules for the client.

Don Smythe Over a year ago

Great, note my use of 'assert' was to use java-like assertion in the client side code during development. For unit-test assertions I am using chai.

thebearingedge Over a year ago

Ah, I see, I will have to keep that approach in mind. Kent C. Dodds has an interesting module called api-check that I have been meaning to look at.

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