#async #mock #smol


Mockable time for use in async runtimes (smol compatibility)

3 releases (breaking)

0.2.0 Jan 22, 2024
0.1.0 Feb 19, 2023
0.0.1 Jan 11, 2023

#390 in Asynchronous

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178 downloads per month

MIT license

229 lines


Asynchronous time mocking for the smol runtime based on async-time-mock-core, inspired by the approach described in Mocking Time In Async Rust.

NOTE: This library is still in it's infancy, the API is still likely to change (read: improve). Please leave your feedback and suggestions on GitHub.

ALSO NOTE: This currently implements an API that looks more like from the tokio runtime instead of smol's Timer API. This might change in the future.

Cargo features

  • mock: Enable the mock clock. If you only enable this in tests, this library turns into a thin wrapper around async-std's time functions.
  • stream: Implement futures_core::stream::Stream for Interval


use async_time_mock_smol::MockableClock;
use std::{
	sync::atomic::{AtomicBool, Ordering},

static HAS_SLEPT: AtomicBool = AtomicBool::new(false);

async fn sleep(clock: MockableClock) {
	// Sleep is either mocked or a real smol::Timer::set_after, depending on which variant of `MockableClock` you pass in.
	let _guard = clock.sleep(Duration::from_secs(3600)).await;
	// Dropping this guard signifies that all the effects of the timer have finished.
	// This allows test code to wait until the condition to assert for has happened.

	println!("Slept for an hour");
	HAS_SLEPT.store(true, Ordering::SeqCst);

fn main() {
		async {
			let (clock, controller) = MockableClock::mock(); // In production, you can use MockableClock::Real instead


			assert!(!HAS_SLEPT.load(Ordering::SeqCst), "Timer won't trigger after just 10 minutes.");

			// advance_time will first trigger the sleep in the task above and then wait until the `_guard` was dropped.
			// This ensures that the task had enough time to actually set `HAS_SLEPT` to `true`.
			assert!(HAS_SLEPT.load(Ordering::SeqCst), "Timer has triggered after 1 hour.")


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