public void TestFindIndex() { List <int> data = new List <int>(Enumerable.Range(0, 100)); var arrayData = data.ToArray(); var enumWrapper = new EnumerableWrapper <int>(data); for (int i = -1; i < 100; i++) { int expected = data.FindIndex(v => v == i); Assert.AreEqual(expected, (data as IEnumerable <int>).FindIndex(v => v == i)); Assert.AreEqual(expected, (arrayData as IEnumerable <int>).FindIndex(v => v == i)); Assert.AreEqual(expected, enumWrapper.FindIndex(v => v == i)); } }