Files/FileList: restore and fix tests

[rodrigoprimo]

Description

This PR restores the FileList tests that were removed in #1213 and fixes the issue that was breaking the ability to run sniff tests for external standards using the PHPCS native test framework.

This problem was happening because self::initializeConfigAndRuleset() was called in a data provider method in AddFileTest.php. This means that the Config instance created inside initializeConfigAndRuleset() using ConfigDouble was created before AllSniffs::suite() had a chance to get the installed standards from the CodeSniffer.conf configuration file. When AllSniffs::suite() runs, ConfigDouble already overrode the configData and configDataFile properties, and
CodeSniffer.conf is never read, and the tests for external standards were not included.

To fix this problem, I opted to change the test to create an instance of the File class (which requires an instance of the Config class) in the test itself instead of doing that in the data provider.

Types of changes

• Bug fix (non-breaking change which fixes an issue)
• New feature (non-breaking change which adds functionality)
• Breaking change (fix or feature that would cause existing functionality to change)
  • This change is only breaking for integrators, not for external standards or end-users.
• Documentation improvement

PR checklist

• I have checked there is no other PR open for the same change.
• I have read the Contribution Guidelines.
• I grant the project the right to include and distribute the code under the BSD-3-Clause license (and I have the right to grant these rights).
• I have added tests to cover my changes.
• I have verified that the code complies with the projects coding standards.
• [Required for new sniffs] I have added XML documentation for the sniff.
• I have opened a sister-PR in the documentation repository to update the Wiki.

[jrfnl]

@rodrigoprimo Could you please re-push the branch ? You changed the base branch after pushing, which means CI will not run the correct checks and the build won't pass.

[rodrigoprimo]

Force pushed without changes to ensure CI runs the correct checks since I changed the base branch after creating the PR.

[jrfnl]

Thanks for this PR @rodrigoprimo. I agree with the analysis. PHPUnit runs the data providers very early on to count the number of tests expected and that appears to be too early for this test.

There are some small things I'd do differently, like drop the assertSame() with the instanceof condition as the else is an assertInstanceOf() anyway; and maybe add a test with a non-File-object, but as this update is only going into the 3.x branch, let's just merge it ;-)