• asyncpg version: 0.20.1
• PostgreSQL version: 12
• Python version: 3.8.2
• Platform: Ubuntu 20.04
• Do you use pgbouncer?: no
• Did you install asyncpg with pip?: yes

I'm using pytest-asyncio for testing some functions that I have. Below an example

# import the pool of connections (already initialized), called db_pool
async def my_fun():
    try:
        async with db_pool.acquire() as conn:
            async with conn.transaction():
                res = await conn.fetchval(query)
    except Exception as e:
        print(e)
        raise e

    return res

I've tested it manually and it works perfectly, but now I'm trying to automate the testing process via pytest and pytest-asyncio.

# import all the stuff that I need
@patch("app.api.db_pool")
@pytest.mark.asyncio
async def test_my_fun(db_pool):
    db_pool.acquire.return_value.__aenter__.transaction.return_value.__aenter__.fetch.return_value = 1

    res = await my_fun()

    assert res == 1

Then I run my tests with
pytest

and I get the following error

>           async with db_pool.acquire() as conn:
E           AttributeError: __aexit__

app/api.py:57: AttributeError
------------------------------------ Captured stdout call ------------------------------------
__aexit__
====================================== warnings summary ======================================
RuntimeWarning: coroutine 'AsyncMockMixin._execute_mock_call' was never awaited
    async with db_pool.acquire() as conn:

================================== short test summary info ===================================
FAILED tests/unit/api.py::test_my_fun - AttributeError: __aexit__

Am I doing tests wrongly or is it a missing feature?

Thanks.