Question

In the following implementation of a hypothetical navigation module the module object returns properties such as isOverBinded or isNavTurnedOff which basically return the consequential value of other methods.

This methods are then utilised in the test cases to check whether a property call has caused its expected consequence.

Should these methods be kept or the original method in question return the consequential values and the same method to be used in the test case?

Currently the code is:

var navModule = (function(element) {

        var nav = {};

        var navHTMLobjs = {

            navList : element,

            listItems : element.find('li'),

            listLinks : element.find('a')

        };

        nav.bindOver = function() {

            navHTMLobjs.navList.on('mouseover mouseout', 'li a', function(e) {

                if (e.type == 'mouseover') {

                    $(this).addClass('over');

                }

                if (e.type == 'mouseout') {

                    $(this).removeClass('over');
                }

            });

        };

        nav.isOverBinded = function(){

            return navHTMLobjs.navList.data('events').hasOwnProperty('mouseover')

                && navHTMLobjs.navList.data('events').hasOwnProperty('mouseout');

        };

        nav.turnOff = function() {

            navHTMLobjs.navList.off('mouseover mouseout');

        };

        nav.isNavTurnedOff = function() {

            return !navHTMLobjs.navList.data.hasOwnProperty('events');

        };

        nav.init = function() {

            this.bindOver();

        };

        return nav;

    });

    var myNav = new navModule($('#nav'));

    /// Test cases:

    module('Navigation module');

    test('Binding total', function() {

        myNav.init();

        equal(myNav.isOverBinded(), true, "Does the init function attach all events?");

    });

    test('Unbinding total', function() {

        myNav.turnOff();

        equal(myNav.isNavTurnedOff(), true, "Does the cancel function correctly unbind events?");

    });

For example should I change nav.bingOver to be:

nav.bindOver = function() {

            navHTMLobjs.navList.on('mouseover mouseout', 'li a', function(e) {

                if (e.type == 'mouseover') {

                    $(this).addClass('over');

                }

                if (e.type == 'mouseout') {

                    $(this).removeClass('over');
                }

            });

            return navHTMLobjs.navList.data('events').hasOwnProperty('mouseover')

                && navHTMLobjs.navList.data('events').hasOwnProperty('mouseout');

        };

…and then use the same method in the test case like below?

test('Binding total', function() {

        myNav.init();

        equal(myNav.bindOver(), true, "Does the init function attach all events?");

    });

What are the differences between the two?

Many thanks

Answer 1

Assuming other parts of the app don’t need to independently verify whether the events have been subscribed to, the bindOver() should not return any value. Also, the isOverBinded() doesnt belong to the navigation module. Its existence is purely to help implement the test. In such a case, that function should be within the testing suite.

var navModule = (function(element) {

    var nav = {};

    var navHTMLobjs = {
        navList : element,
        listItems : element.find('li'),
        listLinks : element.find('a')
    };

    nav.bindOver = function() {
        navHTMLobjs.navList.on('mouseover mouseout', 'li a', function(e) {
            if (e.type == 'mouseover') {
                $(this).addClass('over');
            }

            if (e.type == 'mouseout') {
                $(this).removeClass('over');
            }
        });
    };

    nav.turnOff = function() {
        navHTMLobjs.navList.off('mouseover mouseout');
    };

    nav.init = function() {
        this.bindOver();
    };

    return nav;
});

//var myNav = new navModule($('#nav'));

/// Test cases:

module('Navigation module');

// you might already have such a in memory object 
$root = $('<ul></ul>').append('<li><a href="#"></a></li><li><a href="#"></a></li>'); 
var myNav = new navModule($root);

test('Binding total', function() {

    myNav.init();

    equal(isOverBinded(), true, "Does the init function attach all events?");

});

test('Unbinding total', function() {

    myNav.turnOff();

    equal(isNavTurnedOff(), true, "Does the cancel function correctly unbind events?");

});

var isNavTurnedOff = function() {
    return $root.data('events').hasOwnProperty('mouseover') && $root.data('events').hasOwnProperty('mouseout');
}

var isOverBinded = function() {
    return $root.data.hasOwnProperty('events') === false;
}

At the end of the day I feel, whether or not the function ought to return a value should depend on the usage of the function and not for making testing easier.