Refactor PHPUnitVersionDetector to ease different major version checks

[staabm]

required for phpstan/phpstan-src#4490 (comment)

[ondrejmirtes]

I'd like a PHPUnitVersion class that works the same way PhpVersion works in PHPStan. Methods asking about specific features.

[staabm]

here you are

[ondrejmirtes]

The majorVersion is nullable when we can't detect it? I wonder if we should make the user of PHPUnitVersion explicitly handle it, because otherwise we're basically lying. When we can't detect it, the thing might be supported.

[staabm]

Ok. Adding trinary then

[staabm]

I just had my first mutation testing experience on a phpstan/* repo :)

[ondrejmirtes]

Perfect, thank you!

[ondrejmirtes]

I just had my first mutation testing experience on a phpstan/* repo 😊

Let's record this here: https://github.com/phpstan/phpstan-phpunit/actions/runs/18886595907/job/53903464005

The log will disappear after some time so here's a screenshot:

This is what I had in mind the whole time, I'm glad it pays off 👏