public void WhenAddCalled_ExpectSameValueReturned() { // Arrange var now = DateTime.Now; var addedTimeSpan = TimeSpan.FromDays(15); var expected = now.Add(addedTimeSpan); // Act var target = new DateTimeWrap(now); var actual = target.Add(addedTimeSpan); // Assert actual.DateTimeInstance.Should().Equal(expected); }