Finder unified tests

| Q             | A
| ------------- | ---
| Bug fix?      | [yes]
| New feature?  | [no]
| BC breaks?    | [no]
| Deprecations? | [no]
| Tests pass?   | [yes]
| Fixed tickets | []
| License       | MIT
| Doc PR        | []



This is an attempt to correct problems with tests reported by @fabien in https://github.com/symfony/symfony/pull/7197.

Can someone run the tests on Mac?

The tests on Windows and on TravisCI pass.