Ref #859 (comment)

Instead of using QUnit's extend method to extend a module's env. inheritance, we should improve it with a Object.create's like inheritance.

Suggested by @gibson042:

var createObject = (function( Base ) {
    return function( prototype ) {
        Base.prototype = prototype;
        return new Base();
    };
})( Function() );
…
env = createObject( parentModule.testEnvironment );

We could also use Object.create adding a polyfill that would be used only on IE6~IE8 for the supported browsers.