function createResourceBundleWithCustomBundles(sandbox) {
		var oStub = sandbox.stub(Properties, "create").returns(createFakePropertiesPromise({number: "47", mee: "yo"}));

		var oResourceBundle1;
		var oResourceBundleCustom1;
		var oResourceBundleCustom2;
		return ResourceBundle.create({url: 'my.properties', locale: "en", async: true})
		.then(function(oResourceBundle) {
			oResourceBundle1 = oResourceBundle;
			oStub.returns(createFakePropertiesPromise({number: "45", mec1: "ya"}));

			return ResourceBundle.create({url: 'custom1.properties', locale: "en", async: true});
		})
		.then(function(oResourceBundle) {
			oResourceBundleCustom1 = oResourceBundle;
			oStub.returns(createFakePropertiesPromise({number: "46", mec2: "ye"}));

			return ResourceBundle.create({url: 'custom2.properties', locale: "en", async: true});
		})
		.then(function(oResourceBundle) {
			oResourceBundleCustom2 = oResourceBundle;
			oResourceBundle1._enhance(oResourceBundleCustom1);
			oResourceBundle1._enhance(oResourceBundleCustom2);
			oStub.restore();
			return oResourceBundle1;
		});
	}
@param sandbox
@return {*} ResourceBundle containing CustomBundle1 and CustomBundle2