export declare type Timer = () => number;
/**
 * Returns a function that can be invoked to end
 * the timer and duration.
 */
export declare const createTimer: () => Timer;
/**
 * Determine if a given timer took longer than a given threshold in milliseconds.
 */
export declare const tookLongerThan: (timer: Timer, threshold: number) => boolean;
/**
 * Determine if a given timer took less than a given threshold in milliseconds.
 */
export declare const tookShorterThan: (timer: Timer, threshold: number) => boolean;
export declare const sleep: (ms: number) => Promise<{}>;