public function test_autosave_locked_post() {
    // Lock the post to another user.
    wp_set_current_user( self::$editor_id );
    wp_set_post_lock( self::$post_id );

    wp_set_current_user( self::$admin_id );

    // Ensure post is locked.
    $this->assertEquals( self::$editor_id, wp_check_post_lock( self::$post_id ) );

    // Set up the $_POST request.
    $md5   = md5( uniqid() );
    $_POST = array(
      'action' => 'heartbeat',
      '_nonce' => wp_create_nonce( 'heartbeat-nonce' ),
      'data'   => array(
        'wp_autosave' => array(
          'post_id'      => self::$post_id,
          '_wpnonce'     => wp_create_nonce( 'update-post_' . self::$post_id ),
          'post_content' => self::$post->post_content . PHP_EOL . $md5,
          'post_type'    => 'post',
        ),
      ),
    );

    // Make the request.
    try {
      $this->_handleAjax( 'heartbeat' );
    } catch ( WPAjaxDieContinueException $e ) {
      unset( $e );
    }

    $response = json_decode( $this->_last_response, true );

    // Ensure everything is correct.
    $this->assertNotEmpty( $response['wp_autosave'] );
    $this->assertTrue( $response['wp_autosave']['success'] );

    // Check that the original post was NOT edited.
    $post = get_post( self::$post_id );
    $this->assertStringNotContainsString( $md5, $post->post_content );

    // Check if the autosave post was created.
    $autosave = wp_get_post_autosave( self::$post_id, get_current_user_id() );
    $this->assertNotEmpty( $autosave );
    $this->assertStringContainsString( $md5, $autosave->post_content );
  }