Some useful Jasmine extensions

Friday, Dec 23, 2011 2 minute read Tags: javascript jasmine testing
Hey, thanks for the interest in this post, but just letting you know that it is over 3 years old, so the content in here may not be accurate.

For tbd, a JavaScript helper I’ve written I’ve been using Jasmine for my testing.

Some of the tests I’ve had to go beyond what matchers are available out of the box so I thought I’d share them here (mostly so I’ve got an easy point for myself to find them again :P).

A quick into to adding your own matcher

I’ve you’re new to Jasmine and haven’t added your own matchers here’s a quick tutorial.

You need to use the beforeEach and call addMatchers, like so:

beforeEach(function() {
       alwaysTrue: function(){
           //put your logic in here to determine truthy results
           return true;

Now you can call it like so:


This test extension that I’ve created isn’t really useful as it will always return true but you can put in any logic you want.

The this object has an actual property, which is the value from your expect method and the arguments passed to the call are passed in.

My matchers

beforeEach(function() {
        toBeInArray: function() {
            return ~[];
        toBeInDateRange: function(min, max) {
            var actual = this.actual.getTime();
            return actual <= max.getTime() && actual >= min.getTime();
        toBeInNumericalRange: function (min, max) {
            var actual = this.actual;
            return actual <= max && actual >= min;

Here’s how you use them:

expect('a').toByInArray('a', 'b', 'c');
expect(3).toBeInNumericalRange(0, 10);
expect(new Date(2011, 11, 01)).toBeInDateRange(new Date(2011, 10, 01), new Date(2011, 11, 30));

Hopefully this is helpful to someone else :)