Unit test the /castling command

[programarivm]

This issue is intended to practice software architecture skills as well as unit testing.

As you may have noted, there's a one-to-one correspondence between the Chess\Game methods described in the PHP Chess Docs and the commands available in the chess server:

• ascii(): string <-> ChessServer\Command\AsciiCommand.php
• captures(): array <-> ChessServer\Command\CapturesCommand.php
• castling(): ?array <-> ChessServer\Command\CastlingCommand.php
• ...

All commands should be unit tested in ChessServer\Tests\Unit\Command. However, the ChessServer\Tests\Unit\Command\CastlingTest.php file is missing.

The missing file should be added as per the existing conventions.

Happy learning and coding!

[Pen-y-Fan]

Hi there, happy learning and coding!