[Theory] public static void Invariants (GildedRose gildedRose) {
				Assume.That(gildedRose != null);
				// ReSharper disable once PossibleNullReferenceException
				gildedRose.AssertInvariants();
			}
		public void ResetForTests () {lock (model) {model = GildedRose.MakeExample();}}