wp-includes/rest-api/endpoints/class-wp-rest-site-health-controller.php:271Checks that full page cache is active.
array public function test_page_cache() { $this->load_admin_textdomain(); return $this->site_health->get_test_page_cache(); }Introduced in 6.1.0. Unchanged from 6.7.7 through 7.1.0.
Signature, return type and hooks compared across 5 parsed releases.
src/wp-includes/rest-api/endpoints/class-wp-rest-site-health-controller.php, and regenerated for each WordPress release so it tracks the code rather than a snapshot of it.