A handy utility to add stubbed property on obj, it will be cleaned up automatically. One of the use case is require.js module where it shares a global instance.

stubprop.js

/**
 * Usage:
 *  describe("someModule", function(){
 *      beforeEach(function(){
 *          stubProp(someGlobal, {myVar:'test'});
 *      });
 *  });
 * 
 * - stubProp(obj, {myVar:'value'});
 * - stubProp(obj, 'myVar', 'myValue');
 * */

(function(){

    function getValueMap(name, value){
		var valueMap = name;
		if(typeof name === 'string'){
			valueMap = {};
			valueMap[name] = value;
		}
		return valueMap;
	}
    
	var bin = [];
	function addToBin(obj, name){
		bin.push({obj:obj, name:name});
	}

	this.stubProp = function(obj, name, value){
		var valueMap = getValueMap(name, value);
		for(var key in valueMap){
			if(valueMap.hasOwnProperty(key)){
				obj[key] = valueMap[key];
				addToBin(obj, key);
			}
		}
	};

	afterEach(function(){
		for(var i=0; i<bin.length; i++){
			var entry = bin[i];
			delete entry.obj[entry.name];
		}
		bin = [];
	});

})(this);