public void DateTimeWithHoursMinutesAndSeconds_10DaysAfter_Returns10DaysAfterGivenDate() { var givenDate = new DateTime(2012, 12, 13, 1, 2, 3); var timeSpanTenDays = new TimeSpan(10, 0, 0, 0); DateTime actual = timeSpanTenDays.After(givenDate); var expected = new DateTime(2012, 12, 23, 1, 2, 3); Assert.Equal(expected, actual); }