Wrong namespace in a test class

Problem/Motivation

On a client project, I got a warning during Composer autoloader generation.

Due to a wrong namespace in a test file. As it is in the Search module, I have created an issue for it #3636714: Wrong namespace in test class. This issue is for the search module still in Core on 11.x.

Not sure which one is better between fixing the namespace or moving the files one folder up.

It is not the first warning of this type that I found.

I found one in Config Split, Masquerade, and 2 other modules. I made issues and MR on those modules. But I wonder how such namespace issues are not catched by PHPCS and the other code quality tools.