Add unit tests for _get_cron_lock() function in cron API

tests/phpunit/tests/cron/getCronLock.php

@@ -0,0 +1,103 @@
+<?php
+
+/**
+ * Test the `_get_cron_lock()` function.
+ *
+ * @group cron
+ * @covers ::_get_cron_lock
+ */
+class Tests_Cron_getCronLock extends WP_UnitTestCase {
+
+	/**
+	 * Whether the external object cache was enabled before the test.
+	 *
+	 * @var bool
+	 */
+	private $initial_ext_object_cache;
+
+	/**
+	 * The cron event used to load the executable wp-cron.php file.
+	 *
+	 * @var int
+	 */
+	private $cron_event_timestamp;
+
+	/**
+	 * Sets up the cache state and clears any existing cron lock.
+	 */
+	public function set_up() {
+		parent::set_up();
+
+		$this->initial_ext_object_cache = wp_using_ext_object_cache();
+		delete_option( '_transient_doing_cron' );
+		wp_cache_delete( 'doing_cron', 'transient' );
+
+		$this->cron_event_timestamp = time() - 1;
+		wp_schedule_single_event( $this->cron_event_timestamp, __CLASS__ );
+		set_transient( 'doing_cron', 'different-lock' );
+		$doing_wp_cron = 'test-lock';
+		require_once ABSPATH . 'wp-cron.php';
+		delete_option( '_transient_doing_cron' );
+		wp_cache_delete( 'doing_cron', 'transient' );
+	}
+
+	/**
+	 * Restores the cache state and clears the cron lock after the test.
+	 */
+	public function tear_down() {
+		wp_unschedule_event( $this->cron_event_timestamp, __CLASS__ );
+		delete_option( '_transient_doing_cron' );
+		wp_cache_delete( 'doing_cron', 'transient' );
+		wp_using_ext_object_cache( $this->initial_ext_object_cache );
+
+		parent::tear_down();
+	}
+
+	/**
+	 * Tests that `_get_cron_lock()` returns a stored lock from either storage mechanism.
+	 *
+	 * @ticket 65958
+	 *
+	 * @dataProvider data_get_cron_lock_returns_stored_lock
+	 *
+	 * @param bool   $use_external_cache Whether to use the external object cache.
+	 * @param string $expected           The expected cron lock.
+	 */
+	public function test_get_cron_lock_returns_stored_lock( $use_external_cache, $expected ) {
+		wp_using_ext_object_cache( $use_external_cache );
+		update_option( '_transient_doing_cron', 'database-lock' );
+		wp_cache_set( 'doing_cron', $expected, 'transient' );
+
+		$this->assertSame( $expected, _get_cron_lock() );
+	}
+
+	/**
+	 * Data provider for test_get_cron_lock_returns_stored_lock().
+	 *
+	 * @return array<string, array{
+	 *     use_external_cache: bool,
+	 *     expected: string,
+	 * }>
+	 */
+	public function data_get_cron_lock_returns_stored_lock(): array {
+		return array(
+			'database'       => array(
+				'use_external_cache' => false,
+				'expected'           => 'database-lock',
+			),
+			'external cache' => array(
+				'use_external_cache' => true,
+				'expected'           => 'external-cache-lock',
+			),
+		);
+	}
+
+	/**
+	 * Tests that `_get_cron_lock()` returns zero when no lock is stored.
+	 *
+	 * @ticket 65958
+	 */
+	public function test_get_cron_lock_returns_zero_when_not_set() {
+		$this->assertSame( 0, _get_cron_lock() );
+	}
+}