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Concurrency & performance

asyncio, threading, multiprocessing, and profiling-friendly performance patterns.

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Concurrency & performance medium

How to Mock anyio.run Backends (asyncio vs trio) in Python

Demonstrates how to mock anyio.run to verify backend selection (asyncio or trio) without actually running the event loop.

anyio async testing
Python 
import anyio
from unittest.mock import Mock, patch


async def fetch_data():
    await anyio.sleep(0.1)
    return {"data": 42}


def run_with_backend(backend: str):
    async def main():
        result = await fetch_data()
        print(f"[{backend}] Result: {result}")

    anyio.run(main, backend=backend)


if __nam…
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