[flexcoders] ModuleLoader.child is null

[method_air]

Can anyone explain why ModuleLoader.child is null in the module event 'ready' 
event listener:

this._moduleLoader = new ModuleLoader();
this._moduleLoader.url = "ImageComparisonModule.swf"; // 
                                
this._moduleLoader.addEventListener(ModuleEvent.READY, onReady);

private function onReady(e:ModuleEvent):void
{
     var test:ITest ITest(this._moduleLoader.child); // null                    
}

Module code:

<?xml version="1.0" encoding="utf-8"?>
<s:Module xmlns:fx="http://ns.adobe.com/mxml/2009"; 
                  xmlns:s="library://ns.adobe.com/flex/spark" 
                  xmlns:mx="library://ns.adobe.com/flex/mx" 
                 implements="com.storefront.interfaces.controller.ITest"
                  >
        <fx:Declarations>
                <!-- Place non-visual elements (e.g., services, value objects) 
here -->
        </fx:Declarations>
        
        <s:VGroup width="100%" />
</s:Module>

Cheers,

Philip