public void MutateUnderlyingList(int initialCount) { List <int> original = new List <int>(); for (int i = 0; i < initialCount; i++) { original.Add(i); } ReadOnlyCollection <int> wrapper = ListUtility.AsReadOnly(original); CollectionAssert.AreEqual(original, wrapper); original.Add(original.Count); CollectionAssert.AreEqual(original, wrapper); }