Using RunTests.exe on my build of MF 4.1 (Same test code in later versions), I get a Fail on DataTime_ToStringTest6().
Expected string '07/21/2582 14:12:43', but got '7/21/2582 2:12:43 PM'
The test code prepends '0' to values below 10 for all but the year field.
The MF library does not prepend the 0 and the strings do not compare.
There is also a 12 hr AM/PM clock vs. 24 hr expected by the test code.
On the Desktop MF
DateTime dt = DateTime.Now;
String st = dt.ToString();
Will set st = "8/3/2015 1:34:25 AM".
i,e, Desktop MF will not prepend zeros.
It would appear behaviour matches desktop, and a better unit test is required.