How to mock aiohttp.client.ClientSession.get async context manager

In your link, there is an edit:

EDIT: A GitHub issue mentioned in this post has been resolved and as of version 0.11.1 asynctest supports asynchronous context managers out of the box.

Since asynctest==0.11.1, it was changed, a working example is:

import random
from aiohttp import ClientSession
from asynctest import CoroutineMock, patch

async def get_random_photo_url():
    while True:
        async with ClientSession() as session:
            async with session.get('random.photos') as resp:
                json = await resp.json()
        photos = json['photos']
        if not photos:
            continue
        return random.choice(photos)['img_src']

@patch('aiohttp.ClientSession.get')
async def test_call_api_again_if_photos_not_found(mock_get):   
    mock_get.return_value.__aenter__.return_value.json = CoroutineMock(side_effect=[
        {'photos': []}, {'photos': [{'img_src': 'a.jpg'}]}
    ])

    image_url = await get_random_photo_url()

    assert mock_get.call_count == 2
    assert mock_get.return_value.__aenter__.return_value.json.call_count == 2
    assert image_url == 'a.jpg'

The critical problem is that you need to correctly mock function json as by default it is a MagicMock instance. To get access to this function, you need mock_get.return_value.__aenter__.return_value.json.

The asynctest hasn't received any update since 2020 and one keeps getting the following deprecation notice:

python3.9/site-packages/asynctest/mock.py:434
  python3.9/site-packages/asynctest/mock.py:434: DeprecationWarning: "@coroutine" decorator is deprecated since Python 3.8, use "async def" instead
    def wait(self, skip=0):

Instead MagicMock can be used for mocking the coroutine as mentioned in the documentation:

Setting the spec of a Mock or MagicMock to an async function will result in a coroutine object being returned after calling.

So you could easily use the following:

from unittest.mock import MagicMock

@pytest.mark.asyncio
async def test_download():
    mock = aiohttp.ClientSession
    mock.get = MagicMock()
    mock.get.return_value.__aenter__.return_value.status = 200
    mock.get.return_value.__aenter__.return_value.text.return_value = 'test content'

    async with aiohttp.ClientSession() as session:
        async with session.get('http://test.com') as response:
            assert response.text() == 'test content'

Building on @Sraw 's answer:

@pytest.mark.gen_test
@patch('application.adapters.http_retriever.aiohttp.ClientSession.get')
async def test_get_files(mock_get):

    with open('tests/unit/sample_csv_files/Katapult_mock_response.json','r') as f:
        json_dict = json.load(f)

    mock_get.return_value.__aenter__.return_value.json = CoroutineMock()
    mock_get.return_value.__aenter__.return_value.status = 200
    mock_get.return_value.__aenter__.return_value.json.return_value = json_dict

This worked for me