• Scrutinized tests

• Added useful assertion messages

• Added input and returned types

• Added corresponding headers to be compatible with PHPUnit 9.5.2

• Used assertSame instead of assertEquals

I like this solution because it's readable

The best explanation of filter I have found, online resources just werent making sense to me.

What?
no need for all this,
My code only has 21 lines and I can shorten it to less than 10 lines :).

Wow u make it so smol

It's over engineered, especially now that you've added extra methods that aren't needed.
This kata can be solved with one function containing around 12-20 lines and it will propably be even more readable than this.

Thank you for your answer! Do you have any tips for exploring the rust manual?

Thank you for good comment 🙏🏻

Why do you think this is terrible? 🤔

This is terrible

Super simple and clear.