/**
 * Wraps a function to be executed in the fakeAsync zone:
 * - microtasks are manually executed by calling `flushMicrotasks()`,
 * - timers are synchronous, `tick()` simulates the asynchronous passage of time.
 *
 * If there are any pending timers at the end of the function, an exception will be thrown.
 *
 * ## Example
 *
 * {@example testing/ts/fake_async.ts region='basic'}
 *
 * @param fn
 * @returns {Function} The function wrapped to be executed in the fakeAsync zone
 */
export declare function fakeAsync(fn: Function): Function;
/**
 * Clear the queue of pending timers and microtasks.
 *
 * Useful for cleaning up after an asynchronous test passes.
 *
 * ## Example
 *
 * {@example testing/ts/fake_async.ts region='pending'}
 */
export declare function clearPendingTimers(): void;
/**
 * Simulates the asynchronous passage of time for the timers in the fakeAsync zone.
 *
 * The microtasks queue is drained at the very start of this function and after any timer callback
 * has been executed.
 *
 * ## Example
 *
 * {@example testing/ts/fake_async.ts region='basic'}
 *
 * @param {number} millis Number of millisecond, defaults to 0
 */
export declare function tick(millis?: number): void;
/**
 * Flush any pending microtasks.
 */
export declare function flushMicrotasks(): void;