Python unittest async context manager

How to write unit test for a function with async context managers

async def post_message(url, data, msg_id):
    async with aiohttp.ClientSession() as session:
    try:
        async with session.post(url, json=data, ssl=False) as resp:
            result = await resp.text()
            resp.raise_for_status()
            return msg_id, result, resp.status
    except Exception as e:
        return msg_id, 'Error pushing data', ''

For pytest there is a async testting framework called pytest-asyncio

Given in pypi page on link there is an example code

@pytest.mark.asyncio
async def test_some_asyncio_code():
    res = await library.do_something()
    assert b"expected result" == res

Allowing you to create test for async strutures.

A very very in detail source for test writing with pytest-asyncio

Edit: Here is a colab link you can test the link below I have updated the test code

import pytest
import asyncio
from unittest.mock import AsyncMock, patch
from <your_original_file> import post_message # import your fucntion to test

 # AsyncMock for mock sesion.post and patch to use our mock  insetad of aiohttp.ClientSession()

@pytest.mark.asyncio
async def test_post_message():
    # mock response from service
    mock_resp = AsyncMock()
    mock_resp.text.return_value = "Success"
    mock_resp.status = 200
    mock_resp.__aenter__.return_value = mock_resp

    # post to mock and test if it works as expected
    with patch("aiohttp.ClientSession.post", return_value=mock_resp):
        msg_id, result, status = await post_message("http://test.com", {}, "123")
        assert msg_id == "123"
        assert result == "Success"
        assert status == 200

# Run the test manually
await test_post_message()
print("Test passed")