[Bug]: `ArchTest.php` not running on Windows

What Happened

I have copied the test structure from Pinkary, with an Arch folder and an ArchTest.php file in the root. I have added a new testsuite to phpunit.xml with the folder and file. The file is not included when running pest --arch, until I add it to the testsuite with a backslash.

<testsuite name="Arch">
    <directory>tests/Arch</directory>
    <file>tests/ArchTest.php</file>
    <file>tests\ArchTest.php</file><!-- If I add this it automatically runs on Windows -->
</testsuite>

I believe this to be a Windows issue because of the backward slash. Also, it's possible that it is a PHPUnit issue, but I thought that I'd open it here first and get some feedback.

How to Reproduce

• Install Pinkary project on Windows machine
• Run pest --arch and see that ArchTest.php is not included
• Add <file>tests\ArchTest.php</file> with backslash to testsuite in phpunit.xml
• Run pest --arch again and see that the file is included

Sample Repository

https://github.com/pinkary-project/pinkary.com

Pest Version

3.5.1

PHP Version

8.3.13

Operation System

Windows

Notes

Running without backslash:

❯ pest --arch

   PASS  Tests\Arch\LivewireTest
  ✓ livewire components                                                                                                                                                                                        0.13s  

  Tests:    1 passed (2 assertions)
  Duration: 0.28s

Running with backslash:

❯ pest --arch

   PASS  Tests\Arch\LivewireTest
  ✓ livewire components                                                                                                                                                                                        0.39s  

   PASS  Tests\ArchTest
  ✓ preset → php                                                                                                                                                                                               0.28s  
  ✓ preset → security                                                                                                                                                                                          0.01s  
  ✓ preset → laravel → ignoring 'App\Providers\Filament'                                                                                                                                                       0.12s  

  Tests:    4 passed (43 assertions)
  Duration: 1.08s

Start with the testsuite entries in phpunit.xml and reproduce the issue using pest --arch on Windows with the paths shown. Trace how ArchTest.php is discovered when the path uses forward versus backslashes; done means the file runs without requiring the extra backslash entry.