Repair wp/6.0 branch Actions: use PHPUnit Polyfills' set_up()/tear_down() fixture methods - #383

What?

Fixes a fatal error, identical across all six PHP 7.4/8.0/8.1 (single-site and multisite) unit-test.yml legs, that blocks PHPUnit from even starting the test suite.

Why?

#380 (the base of this PR) bumped wp-phpunit/wp-phpunit to 6.0.x to fix a different, unrelated PHPUnit-startup gate. That bump changed WP_UnitTestCase's own ancestry: it now chains through yoast/phpunit-polyfills, whose TestCase class seals setUp()/tearDown() (and the static setUpBeforeClass()/tearDownAfterClass()) with a : void return type, and instead expects subclasses to override the snake_case set_up()/tear_down()/set_up_before_class()/tear_down_after_class() methods — a deliberate Polyfills design that keeps fixture methods callable on PHP versions that predate the void return type.

Nine test classes in this repository still declare the old camelCase fixture methods with no return type, which PHP treats as an incompatible override of the parent's typed declaration:

Fatal error: Declaration of WP_Block_Supports_Layout_Test::setUp() must be compatible with
Yoast\PHPUnitPolyfills\TestCases\TestCase::setUp(): void in phpunit/block-supports/layout-test.php

This is fatal on every PHP-version leg where PHP itself supports typed return declarations (7.1+), which covers 7.4/8.0/8.1 of the current matrix.

How?

Renames each affected method to its Polyfills-expected name, including the corresponding parent:: call where one exists. Checked each of the 9 files individually rather than assuming a uniform pattern — some notable differences found along the way:

• phpunit/class-wp-webfonts-local-provider-test.php already had a correctly-named tear_down(); only its setUp() needed renaming.
• phpunit/navigation-test.php's setUp()/tearDown() never call parent::setUp()/parent::tearDown(), so only the method names themselves needed changing.
• phpunit/navigation-page-test.php is the only file with static setUpBeforeClass()/tearDownAfterClass() overrides in addition to the instance methods — all four needed renaming.
• phpunit/class-wp-test-rest-users-controller.php also defines wpSetUpBeforeClass()/wpTearDownAfterClass() — a separate, WP-specific factory convention (not PHPUnit's own fixture methods) — left untouched.

Testing

php -l passes on all 9 changed files. Real CI evidence: triggered a run on this PR and confirmed the specific Declaration of ... setUp() must be compatible with ... TestCase::setUp(): void fatal error no longer occurs on the previously-failing PHP 7.4/8.0/8.1 legs.

Use of AI Tools

This PR was created by Claude Code under my supervision. All code should be treated as AI-produced and not yet reviewed by a human until this PR is marked Ready for Review.