diff --git a/tests/phpunit/tests/admin/includes/ajax-actions/menuGetMetabox.php b/tests/phpunit/tests/admin/includes/ajax-actions/menuGetMetabox.php
new file mode 100644
index 0000000000000..fba5408041c43
--- /dev/null
+++ b/tests/phpunit/tests/admin/includes/ajax-actions/menuGetMetabox.php
@@ -0,0 +1,172 @@
+<?php
+
+/**
+ * Admin Ajax functions to be tested.
+ */
+require_once ABSPATH . 'wp-admin/includes/ajax-actions.php';
+
+/**
+ * Testing wp_ajax_menu_get_metabox() functionality.
+ *
+ * @package WordPress
+ * @subpackage UnitTests
+ * @since 3.1.0
+ *
+ * @group ajax
+ *
+ * @covers ::wp_ajax_menu_get_metabox
+ */
+class Tests_wp_ajax_menu_get_metabox extends WP_Ajax_UnitTestCase {
+
+	/**
+	 * Administrator user ID.
+	 *
+	 * @var int
+	 */
+	protected static $admin_id;
+
+	/**
+	 * Subscriber user ID.
+	 *
+	 * @var int
+	 */
+	protected static $subscriber_id;
+
+	/**
+	 * Setup test fixtures.
+	 *
+	 * @param WP_UnitTest_Factory $factory
+	 */
+	public static function wpSetUpBeforeClass( WP_UnitTest_Factory $factory ): void {
+		self::$admin_id      = $factory->user->create( array( 'role' => 'administrator' ) );
+		self::$subscriber_id = $factory->user->create( array( 'role' => 'subscriber' ) );
+	}
+
+	/**
+	 * Tests retrieval of post type metabox.
+	 *
+	 * @ticket 65252
+	 */
+	public function test_menu_get_metabox_post_type(): void {
+		wp_set_current_user( self::$admin_id );
+
+		self::factory()->post->create(
+			array(
+				'post_title' => 'Post Metabox Test',
+			)
+		);
+
+		$_POST = array(
+			'action'      => 'menu-get-metabox',
+			'item-type'   => 'post_type',
+			'item-object' => 'post',
+		);
+
+		try {
+			$this->_handleAjax( 'menu-get-metabox' );
+		} catch ( WPAjaxDieContinueException $e ) {
+			// We expect the function to die after echoing JSON.
+		}
+
+		$response = json_decode( $this->_last_response, true );
+
+		$this->assertIsArray( $response );
+		$this->assertSame( 'posttype-post', $response['replace-id'] );
+		$this->assertStringContainsString( 'id="posttype-post"', $response['markup'] );
+		$this->assertStringContainsString( 'Post', $response['markup'] );
+	}
+
+	/**
+	 * Tests retrieval of taxonomy metabox.
+	 *
+	 * @ticket 65252
+	 */
+	public function test_menu_get_metabox_taxonomy(): void {
+		wp_set_current_user( self::$admin_id );
+
+		$_POST = array(
+			'action'      => 'menu-get-metabox',
+			'item-type'   => 'taxonomy',
+			'item-object' => 'category',
+		);
+
+		try {
+			$this->_handleAjax( 'menu-get-metabox' );
+		} catch ( WPAjaxDieContinueException $e ) {
+			// We expect the function to die after echoing JSON.
+		}
+
+		$response = json_decode( $this->_last_response, true );
+
+		$this->assertIsArray( $response );
+		$this->assertSame( 'taxonomy-category', $response['replace-id'] );
+		$this->assertStringContainsString( 'id="taxonomy-category"', $response['markup'] );
+		$this->assertStringContainsString( 'Categories', $response['markup'] );
+	}
+
+	/**
+	 * Tests failure due to insufficient permissions.
+	 *
+	 * @ticket 65252
+	 */
+	public function test_menu_get_metabox_insufficient_permissions(): void {
+		wp_set_current_user( self::$subscriber_id );
+
+		$_POST = array(
+			'action'      => 'menu-get-metabox',
+			'item-type'   => 'post_type',
+			'item-object' => 'post',
+		);
+
+		$this->expectException( WPAjaxDieStopException::class );
+		$this->expectExceptionMessage( '-1' );
+
+		$this->_handleAjax( 'menu-get-metabox' );
+	}
+
+	/**
+	 * Tests behavior with invalid item-type.
+	 *
+	 * @ticket 65252
+	 */
+	public function test_menu_get_metabox_invalid_item_type(): void {
+		wp_set_current_user( self::$admin_id );
+
+		$_POST = array(
+			'action'      => 'menu-get-metabox',
+			'item-type'   => 'invalid',
+			'item-object' => 'post',
+		);
+
+		try {
+			$this->_handleAjax( 'menu-get-metabox' );
+		} catch ( WPAjaxDieStopException $e ) {
+			// We expect it to die without outputting anything if item-type is invalid.
+		}
+
+		$this->assertEmpty( $this->_last_response );
+	}
+
+	/**
+	 * Tests behavior with invalid item-object.
+	 *
+	 * @ticket 65252
+	 */
+	public function test_menu_get_metabox_invalid_item_object(): void {
+		wp_set_current_user( self::$admin_id );
+
+		$_POST = array(
+			'action'      => 'menu-get-metabox',
+			'item-type'   => 'post_type',
+			'item-object' => 'non_existent_post_type',
+		);
+
+		try {
+			$this->_handleAjax( 'menu-get-metabox' );
+		} catch ( WPAjaxDieStopException $e ) {
+			// We expect it to die without outputting anything if item-object is invalid.
+		}
+
+		$this->assertEmpty( $this->_last_response );
+	}
+}