public void IndexOfItems()
        {
            var list = new HistoryObjectListHistory <MockHistoryObject>(FromId)
            {
                new MockHistoryObject(0),
                new MockHistoryObject(1),
                new MockHistoryObject(2),
                new MockHistoryObject(3),
                new MockHistoryObject(4),
                new MockHistoryObject(5),
            };

            Assert.AreEqual(0, list.IndexOf(new MockHistoryObject(0)));
            Assert.AreEqual(1, list.IndexOf(new MockHistoryObject(1)));
            Assert.AreEqual(2, list.IndexOf(new MockHistoryObject(2)));
            Assert.AreEqual(3, list.IndexOf(new MockHistoryObject(3)));
            Assert.AreEqual(4, list.IndexOf(new MockHistoryObject(4)));
            Assert.AreEqual(5, list.IndexOf(new MockHistoryObject(5)));
        }