Tests: Add unit tests for wp_is_maintenance_mode()

[shail-mehta]

What

Trac ticket: #65819

Adds unit tests for wp_is_maintenance_mode() in tests/phpunit/tests/load/wpIsMaintenanceMode.php.

Covers a missing/expired .maintenance file, a fresh file, installing mode, scrape credentials, and the enable_maintenance_mode filter.

Test-only change.

Why

This helper has had no dedicated PHPUnit coverage. Fits the #65819 missing-coverage track, and no open PR covers it.

How

• Write and delete a temporary .maintenance file in tear_down()
• Assert fresh timestamps enable maintenance mode, and missing/expired files do not
• Cover installing mode, scrape key/nonce bypass, and the enable_maintenance_mode filter

Testing instructions

npm run test:php -- --filter Tests_Load_WpIsMaintenanceMode

Use of AI Tools

• Cursor

[Copilot]

🟢 Approval recommended

The tests match the helper’s behavior, include cleanup, and have no identified blocking issues.

No open issues 🎉

What changed in this PR

Adds dedicated PHPUnit coverage for wp_is_maintenance_mode() as part of ticket #65819, without changing production code.

Changes:

• Tests missing, fresh, and expired maintenance files.
• Covers installation mode, scrape credentials, and filter behavior.
• Adds fixture cleanup and state restoration.

File	Description
tests/​phpunit/​tests/​load/​wpIsMaintenanceMode.php	Adds maintenance-mode tests and fixture lifecycle helpers.

_{Review effort: Balanced}

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[mukeshpanchal27]

Optional note: this writes a real .maintenance file into ABSPATH, because wp_is_maintenance_mode() hard-codes that path. tear_down() removes it. If a run stops partway, though, the file stays, and the next bootstrap would stop in maintenance mode for up to 10 minutes. A short comment here would help the next person who sees that.