private static void CheckFarm(XmlNode fieldNode, Field field, Catalog catalog)
{
var farmId = fieldNode.GetXmlAttribute("F");
if (String.IsNullOrEmpty(farmId))
return;
var farm = catalog.Farms.Single(f => f.Id.ReferenceId == field.FarmId);
Assert.AreEqual(farmId, farm.Id.FindIsoId());
}