public static IEnumerable<object[]> Add_TimeSpan_TestData()
{
yield return new object[] { new DateTimeOffset(new DateTime(1000, DateTimeKind.Utc)), new TimeSpan(10), new DateTimeOffset(new DateTime(1010, DateTimeKind.Utc)) };
yield return new object[] { new DateTimeOffset(new DateTime(1000, DateTimeKind.Utc)), TimeSpan.Zero, new DateTimeOffset(new DateTime(1000, DateTimeKind.Utc)) };
yield return new object[] { new DateTimeOffset(new DateTime(1000, DateTimeKind.Utc)), new TimeSpan(-10), new DateTimeOffset(new DateTime(990, DateTimeKind.Utc)) };
}