/**
 * @license Copyright (c) 2003-2026, CKSource Holding sp. z o.o. All rights reserved.
 * For licensing, see LICENSE.md or https://ckeditor.com/legal/ckeditor-licensing-options
 */
/**
 * @module utils/spy
 */
/**
 * Creates a spy function (ala Sinon.js) that can be used to inspect call to it.
 *
 * The following are the present features:
 *
 * * spy.called: property set to `true` if the function has been called at least once.
 *
 * @returns The spy function.
 */
export declare function spy(): {
    (): void;
    called?: boolean;
};