function xml(assert, sXml) {
		var oDocument = XMLHelper.parse(sXml);

		assert.strictEqual(oDocument.parseError.errorCode, 0, "XML parsed correctly");
		return oDocument;
	}
Creates a DOM document from the given string.
@param {object} assert the assertions
@param {string} sXml the XML as string
@returns {Document} the DOM document