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Asyncio Time Travel Loop

Project description

Asyncio Time Travel Loop


Asyncio Time Travel Loop allows you to test asyncio code that waits or sleeps, without actually waiting or sleeping.

At the same time, you don't have to bother thinking about how the time advances. Your code should work exactly the same with TimeTravelLoop as it works with a normal asyncio events loop.

Example: Assume that you have a code that waits 1000 seconds, and you want to tests that code. Instead of actually waiting 1000 seconds, you could use TimeTravelLoop:

import asyncio
from asyncio_time_travel import TimeTravelLoop


tloop = TimeTravelLoop()

async def inner_coro():
    # Sleep for a long time:
    await asyncio.sleep(SLEEP_TIME, loop=tloop)


This code completes immediately.

See some of the tests for more advanced examples of what TimeTravelLoop can do.



pip install asyncio-time-travel

You can also find the package at .


Run (Inside asyncio_time_travel dir):


If you haven't yet heard of pytest, it's your lucky day :)

How does this work?

TimeTravelLoop source is based on the source code of asyncio.test_utils.TestLoop.

For each _run_once iteration of the loop, the following is done:

  • Loop events are executed.
  • Time is advanced to the closest scheduled event.

Using this method your code never waits, and at the same time the events execute in the correct order.


TimeTravelLoop is meant to be used with your tests, not for production code. In particular, if your loop interacts with external events, bending time is not a good idea (Time will advance differently outside of your loop).

Further work

  • The code might have bugs. If you find any issues, don't hesitate to fork or open an issue.

  • It might be possible to integrate this code into asyncio.test_utils in some way.

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