Basic BDD example for addClass method

addClass.js

/**
 * Experimenting with no frills BDD to write a simple addClass method
 */

function TestSuite(name, setup, teardown) {       
    var leftPadding = 60;
    
    this.name = name || '';
    this.tests = [];           
    this.setup = setup || function() {},
    this.teardown = teardown || function() {};
    
    this.addTest = function(description, tests) {
        this.tests.push(function() {
            console.log(description + ' =>' + (function(num) { var pad = ''; while(num--) { pad += ' '; } return pad; })(leftPadding-description.length), tests() ? 'pass' : 'fail');
        });
        
        return this;        
    };               
    
    this.run = function() {   
        this.name && console.log(this.name + ' Test Suite')
        for(var i=0; i<this.tests.length; i++) {
            this.setup();
            this.tests[i]();
            this.teardown();
        }           
        
        return this;
    }
};    

function addClass(elem, newClassName) {
    var className, classes, classesLength;
    
    if(typeof elem === 'string') {
        elem = document.getElementById(elem);
    }

    if(elem === null || elem.nodeType !== 1 || typeof newClassName !== 'string') {
        return null;
    }  
    className = elem.className;

    classes = newClassName.split(' '),
    classIndex = classes.length;

    while(classIndex--) {
        className = (className.match(new RegExp('\\b'+classes[classIndex]+'\\b')) === null ? className +' '+ classes[classIndex] : className); 
    }              
                                           
    elem.className = className;
	return elem;
}

(function() {   
     
	var element = {
    		className: 'top left float'
    	},     
    	
    	setup = function() {
            document.body.appendChild(
        		 (function() {
    				var e = document.createElement('div');
    				e.setAttribute('id', 'addClassTest'); 
    				e.className = element.className;
    				e.innerHTHML = 'Ryan\'s Test Div';
    				return e;
    			})()
    		);
    	},   
    	
    	teardown = function() {
    	    document.body.removeChild(document.getElementById('addClassTest'));
    	};
    	
    	new TestSuite('addClass', setup, teardown)
    	    .addTest('Resolves element by id if string passed in for elem', function() {
    	        return addClass('addClassTest', 'test') !== null;
    	    })                                 
    	    
    	    .addTest('Returns null if non-existent id string passed in for elem', function() {
    	        return addClass('WTF', 'test') === null;
    	    })    
    	    
    	    .addTest('Does not add duplicate classes (single class)', function() {
    	        return addClass('addClassTest', 'top').className == element.className;
    	    })   
    	    
    	    .addTest('Does not add duplicate classes (mulitple classes)', function() {
    	        return addClass('addClassTest', 'top float').className == element.className;
    	    })
    	         
    	    .addTest('Adds new classes', function() {
    	        return addClass('addClassTest', 'newClass').className == element.className + ' newClass';
    	    })   
    	    
    	    .addTest('Adds new classes (multiple classes)', function() {
    	        return addClass('addClassTest', 'newClass otherNewClass').className.split(' ').length == element.className.split(' ').length + 2;
    	    })   
    	           
    	    .run();
})();