Filesystem API: Add initial tests for WP_Filesystem_Direct.

[costdev]

This adds some initial tests for the WP_Filesystem_Direct filesystem abstraction class.

These tests do not aim to cover all paths, but to add line/branch coverage where source changes are not needed to facilitate testing or resolve bugs. The intention is to make it easier to know how to hit a line/branch when trying to cover paths in future.

This also introduces the WP_Filesystem_Direct_UnitTestCase class, which contains shared properties, set_up()/tear_down(), helpers and common data providers for the tests.

To allow constants to be set without affecting other tests in the test suite, some of these tests use the @runInSeparateProcess annotation [Ref]. To prevent an exception for Serialization of 'Closure' is not allowed, the @preserveGlobalState disabled annotation is also used [Ref].

Tests exist for the following methods:

• __construct()
• get_contents()
• get_contents_array()
• put_contents()
• cwd()
• chdir()
• chgrp()
• chmod()
• chown()
• getchmod()
• copy()
• move()
• delete()
• exists()
• is_file()
• is_dir()
• is_readable()
• is_writable()
• atime()
• mtime()
• size()
• touch()
• mkdir()
• rmdir()
• dirlist()

Trac ticket: https://core.trac.wordpress.org/ticket/57774

[costdev]

Note:

• setMethods() is deprecated in PHPUnit 9 and removed in PHPUnit 10.
• The suitable replacement for this case and others in this PR is onlyMethods(), introduced in PHPUnit 8.3.0.
• However, as the WP Core test suite runs in PHP 5.6, this uses an earlier version of PHPUnit, so setMethods() must be used.
• It may be preferable to add a PHP or PHPUnit version check here and run the appropriate method, so that compatibility with PHPUnit 10+ can be achieved without being coupled to the minimum WP Core version run in the test suite, or this could be done later to address all uses of setMethods() in the test suite in one go.

[swissspidy]

Related: Yoast/PHPUnit-Polyfills#58

[costdev]

Further testing requires more investigation for stable testing. This includes a source change to support detecting root as the user to prevent test failures in local test runners for methods such as ::owner() and ::group() when root is the user. The results of further investigation, and the above source change will be proposed in separate tickets/PRs.

🔢 Applies elsewhere in the tests / WP_Filesystem_Direct class.

[github-actions]

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Props swissspidy, costdev, mukesh27.

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[swissspidy]

Merged in https://core.trac.wordpress.org/changeset/57753

[github-actions]

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