/** Ask the OS for an unused ephemeral port. */
export declare function getFreePort(): Promise<number>;
/** True if something already accepts TCP connections on the port (e.g. a dev server). */
export declare function isPortListening(port: number, host?: string): Promise<boolean>;
/** Poll the app for any non-5xx HTTP response until it's ready or the timeout hits. */
export declare function waitForApp(port: number, timeoutMs: number): Promise<boolean>;