How to unit test DOM manipulation (with jasmine)

I’ve been using a helpful addition to jasmine called jasmine-jquery available on github.

It gives you access to a number of useful extra matcher functions, to assert jquery objects and their properties.

In particular the features I have found useful so far are asserting on attributes of dom elements, and spying on events such as clicks and submits…

Here is a somewhat contrived example… 🙂

describe("An interactive page", function() {
    it("'s text area should not contain any text before pressing the button", function() {
        expect(Page.textArea).toBeEmpty();
    });

    it("should contain a text area div", function() {
        expect(Page.textArea).toBe('div#textArea');
    });

    it("should append a div containing a random string to the text area when clicking the button", function() {
        var clickEvent = spyOnEvent('#addTextButton', 'click');
        $('button#addTextButton').click();

        expect('click').toHaveBeenTriggeredOn('#addTextButton');
        expect(clickEvent).toHaveBeenTriggered();

        expect($('div.addedText:last')).not.toBeEmpty());
    });
});

and here is the code:

var Page = {
    title : 'a title',
    description : 'Some kind of description description',
    textArea : $('div#textArea'),
    addButton : $('button#addTextButton'),


    init : function() {
        var _this = this;
        this.addButton.click(function(){
        var randomString = _this.createRandomString();
            _this.addTextToPage(randomString);
        });
    },

    addTextToPage : function( text ) {
        var textDivToAdd = $('<div>').html('<p>'+text+'</p>');

        this.textArea.append( textDivToAdd );
    },

    createRandomString : function() {
        var text = "";
        var possible = "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789";

        for( var i=0; i < 5; i++ )
             text += possible.charAt(Math.floor(Math.random() * possible.length));

        return text;
    },
};

Page.init();

I’ve found jasmine to be really flexible and agreeable to use so far, I always appreciate pointers for making it the code better though!