JSFiddle - React, Tailwind, and code Playground

HTML

<script src="http://yui.yahooapis.com/3.5.0pr1/build/yui/yui-min.js"></script>
<div id="console" class="yui3-skin-sam"></div>

JavaScript

YUI().use('app-base', 'test', 'test-console', function (Y) {

    var suite = new Y.Test.Suite('App showView() callback');
    
    suite.add(new Y.Test.Case({
        name: 'App showView() callback',
        
        'showView() should call the specified callback when the views are different': function () {
            var app   = new Y.App(),
                count = 0;
            
            app.showView(new Y.View(), null, function () {
                count += 5;
            });
            
            app.showView(new Y.View(), null, function () {
                count += 1;
            });
            
            Y.Assert.areSame(2, count);
        },
        
        'showView() should call the specified callback when the views are different': function () {
            var app   = new Y.App(),
                view  = new Y.View(),
                count = 0;
            
            app.showView(view, null, function () {
                count += 5;
            });
            
            app.showView(view, null, function () {
                count += 1;
            });
            
            Y.Assert.areSame(2, count);
        }
    }));
    
    new Y.Test.Console().render('#console');
    Y.Test.Runner.add(suite);
    Y.Test.Runner.run();
    
});