public void CalculatePersistence_OnKnowns_ShouldReturnProperResults(ulong input, int expected)
        {
            var persistence = new Persistence();

            persistence.CalculatePersistence(input).Should().Be(expected);
        }
        public void PersistNumberphileNumber_ShouldHavePersistenceOf11()
        {
            var persistence = new Persistence();

            persistence.CalculatePersistence(277777788888899).Should().Be(11);
        }