Add tests for ByteArrayExtensions

[M-Zuber]

Fixed up some bugs found while testing.
Added UTF32 Big Endian
Closes #4

[vladislav-karamfilov]

Using the file system for unit tests is not cool. In your case a better approach would be to use Encoding.<SomeEncoding>.GetBytes() method for getting the bytes of a string.

[M-Zuber]

Arguable, but you have a point.
Will verify in the morning that ...GetBytes() returns the proper encoding markers also, to make sure it is testing a as close to real life situation as possible.
If so will gladly update the PR.

While I have your attention, any thoughts on how to identify a UTF16 file with zero in first two bytes after marking as opposed to thinking it is UTF32?

[M-Zuber]

@Teodor92 fixed the issue with using the FS in the tests.

[vladislav-karamfilov]

@M-Zuber, I can't think of a better approach than the additional check bytes.Length % 4 == 0 added to the check for UTF-32. UTF-32 encoding is 4 bytes fixed-width and UTF-16 is variable 2 or 4 bytes so the check won't catch all cases correct but the change of getting the correct encoding is higher.

PS I'm sorry for my late answer. I was very busy last week...
PS2 Good job removing the file system dependency! 👍

[M-Zuber]

@vladislav-karamfilov thanks for the tip, added a check + test for a UTF16 buffer with leading zeros.

So this should be finished and ready to merge

[vladislav-karamfilov]

Small typos:
fixed with -> fixed width
UTF16 -> UTF-16
UTF 16 -> UTF-16
UTF32 -> UTF-32

Also UTF-16 is has variable width of 2 or 4 bytes. It's good to update the comment. 😸

[vladislav-karamfilov]

It looks good to me. Just a few improvements in a comment and I can merge it. :-)

[M-Zuber]

Comments updated. Thanks.