MagicMock doesn't implement `aenter` or `aexit` #29

txomon · 2016-12-19T23:24:21Z

When testing asyncio code, the probability of needing to test async context manager is high.

The current code using MagicMock doesn't implement __aenter__ or __aexit__ methods

The text was updated successfully, but these errors were encountered:

Martiusweb · 2016-12-20T09:20:12Z

Hi,

Thanks for the report, it's on the todo list!

Gr1N · 2016-12-20T13:55:56Z

+1 it would be really useful to add implementation of __aenter__ and __aexit__ methods.

txomon · 2016-12-20T14:41:27Z

I add this link as relevant to the conversation http://bugs.python.org/issue26467

serg666 · 2017-01-27T20:14:44Z

Hi, guys! Any news about this issue?

serg666 · 2017-01-27T20:52:50Z

I would like to mock aiopg.sa.create_engine with CoroutineMock, but if I use async-with-style it does not work

import asyncio
import aiopg.sa
import asynctest


mock = asynctest.CoroutineMock()

async def create_engine():
    kwargs = {'echo': True}
    return await aiopg.sa.create_engine(
        'dbname=db user=user password=pass host=127.0.0.1',
        **kwargs
   )

async def go(get_engine):
    engine = await get_engine()
    async with engine.acquire() as conn:
        async with conn.begin():
            r = await conn.execute('SELECT version();')
    return await r.fetchone()

row = asyncio.get_event_loop().run_until_complete(go(create_engine))
print(row)

row = asyncio.get_event_loop().run_until_complete(go(mock))
print(row)

python atest.py 
('PostgreSQL 9.6.1 on x86_64-suse-linux-gnu, compiled by gcc (SUSE Linux) 6.2.1 20161209 [gcc-6-branch revision 243481], 64-bit',)
Traceback (most recent call last):
  File "atest.py", line 25, in <module>
    row = asyncio.get_event_loop().run_until_complete(go(mock))
  File "/usr/lib64/python3.5/asyncio/base_events.py", line 337, in run_until_complete
    return future.result()
  File "/usr/lib64/python3.5/asyncio/futures.py", line 274, in result
    raise self._exception
  File "/usr/lib64/python3.5/asyncio/tasks.py", line 239, in _step
    result = coro.send(None)
  File "atest.py", line 17, in go
    async with engine.acquire() as conn:
AttributeError: __aexit__

but if I do not use async-with-style all works fine

import asyncio
import aiopg.sa
import asynctest


mock = asynctest.CoroutineMock()

async def create_engine():
    kwargs = {'echo': True}
    return await aiopg.sa.create_engine(
        'dbname=wallet user=wallet password=qazwsx host=127.0.0.1',
        **kwargs
   )

async def go(get_engine):
    engine = await get_engine()
    conn = await engine.acquire()
    trans = await conn.begin()
    r = await conn.execute('SELECT version();')
    await trans.commit()
    engine.release(conn)
    return await r.fetchone()

row = asyncio.get_event_loop().run_until_complete(go(create_engine))
print(row)

row = asyncio.get_event_loop().run_until_complete(go(mock))
print(row)

('PostgreSQL 9.6.1 on x86_64-suse-linux-gnu, compiled by gcc (SUSE Linux) 6.2.1 20161209 [gcc-6-branch revision 243481], 64-bit',)
<CoroutineMock name='mock.......' id='139844439568168'>

Galbar · 2017-03-21T16:21:30Z

We had the same problem mocking aiopg. We ended up with this workaround:

class AsyncContextManagerMock(MagicMock):

    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)

        for key in ('aenter_return', 'aexit_return'):
            setattr(self, key,  kwargs[key] if key in kwargs else MagicMock())

    async def __aenter__(self):
        return self.aenter_return

    async def __aexit__(self, *args):
        return self.aexit_return

Martiusweb · 2017-03-28T08:43:01Z

Hello,

Some news regarding this issue: I'm working on a solution which seems to be working for the basic needs (in the async_with branch). Some cases are yet to be tested, but if some of you want to try it, feedback is welcome.

serg666 · 2017-03-30T09:49:00Z

Hello, @Martiusweb !

Do you mean async_magic branch ?

Martiusweb · 2017-03-30T09:50:39Z

Yes, I mean async_magic (https://github.com/Martiusweb/asynctest/tree/async_magic).

serg666 · 2017-03-30T09:59:37Z

I have just try async_magic branch with code as below

import asyncio
import aiopg.sa
import asynctest


mock = asynctest.CoroutineMock()

async def create_engine():
    kwargs = {'echo': True}
    return await aiopg.sa.create_engine(
        'dbname=db user=dbuser password=qazwsx host=127.0.0.1',
        **kwargs
   )

async def go(get_engine):
    engine = await get_engine()
    async with engine.acquire() as conn:
        async with conn.begin():
            r = await conn.execute('SELECT version();')
    return await r.fetchone()

row = asyncio.get_event_loop().run_until_complete(go(create_engine))
print(row)

row = asyncio.get_event_loop().run_until_complete(go(mock))
print(row)

I have got the following:

python atest.py
('PostgreSQL 9.6.2 on x86_64-suse-linux-gnu, compiled by gcc (SUSE Linux) 6.3.1 20170202 [gcc-6-branch revision 245119], 64-bit',)
Traceback (most recent call last):
File "atest.py", line 25, in
row = asyncio.get_event_loop().run_until_complete(go(mock))
File "/usr/lib64/python3.6/asyncio/base_events.py", line 466, in run_until_complete
return future.result()
File "atest.py", line 17, in go
async with engine.acquire() as conn:
TypeError: object MagicMock can't be used in 'await' expression

Martiusweb · 2017-03-30T11:46:17Z

This is because asynctest has no way to know that engine.acquire() is a coroutine, hence it's mocked as a MagicMock rather than a CoroutineMock.

However, it worked before because CoroutineMock returned an other CoroutineMock as the result of its invocation, which is wrong.

You can fix this by doing something like:

engine_mock = asyncio.MagicMock(Engine())
mock = asyncio.CoroutineMock(return_value=engine_mock)

serg666 · 2017-03-30T11:56:57Z

import asyncio
import aiopg.sa
import asynctest


mock = asynctest.CoroutineMock(return_value=asynctest.MagicMock())

async def create_engine():
    kwargs = {'echo': True}
    return await aiopg.sa.create_engine(
        'dbname=db user=dbuser password=qazwsx host=127.0.0.1',
        **kwargs
   )

async def go(get_engine):
    engine = await get_engine()
    async with engine.acquire() as conn:
        async with conn.begin():
            r = await conn.execute('SELECT version();')
    return await r.fetchone()

row = asyncio.get_event_loop().run_until_complete(go(create_engine))
print(row)

row = asyncio.get_event_loop().run_until_complete(go(mock))
print(row)

python atest.py
('PostgreSQL 9.6.2 on x86_64-suse-linux-gnu, compiled by gcc (SUSE Linux) 6.3.1 20170202 [gcc-6-branch revision 245119], 64-bit',)
Traceback (most recent call last):
File "atest.py", line 26, in
row = asyncio.get_event_loop().run_until_complete(go(mock))
File "/usr/lib64/python3.6/asyncio/base_events.py", line 466, in run_until_complete
return future.result()
File "atest.py", line 18, in go
async with engine.acquire() as conn:
TypeError: object MagicMock can't be used in 'await' expression

Martiusweb · 2017-03-30T12:00:55Z

That's still the same issue: asynctest can't know that the MagicMock (without spec) returned by mock() must have an aquire attribute which is a Coroutine.

This:

mock = asynctest.CoroutineMock(return_value=asynctest.MagicMock())

is already equivalent to the default behavior, but you can do this:

mock = asynctest.CoroutineMock()
mock().acquire = CoroutineMock()  # which tells that acquire is a coroutine.

(edited: first sentence was incomplete)

serg666 · 2017-04-11T09:19:24Z

Ok. I just modify code like this

import asyncio
import aiopg.sa
import asynctest


def make_engine(connection):
    return asynctest.CoroutineMock(
        return_value=asynctest.CoroutineMock(
            acquire=asynctest.CoroutineMock(
                return_value=connection
            )
        )
    )

async def create_engine():
    kwargs = {'echo': True}
    return await aiopg.sa.create_engine(
        'dbname=dbname user=dbuser password=dbpassword host=127.0.0.1',
        **kwargs
   )

async def go(get_engine):
    engine = await get_engine()
    print(engine.acquire)
    print(asyncio.iscoroutinefunction(engine.acquire))
    print(asyncio.iscoroutine(engine.acquire()))
    async with engine.acquire() as conn:
        async with conn.begin():
            r = await conn.execute('SELECT version();')
    return await r.fetchone()


#row = asyncio.get_event_loop().run_until_complete(go(create_engine))
#print(row)

row = asyncio.get_event_loop().run_until_complete(go(make_engine(asynctest.CoroutineMock())))
print(row)

so, mock have an acquire attribute which is a Coroutine.

but any way I have got the following:

python atest.py 
<CoroutineMock name='mock.acquire' id='140187495530904'>
True
True
Traceback (most recent call last):
  File "atest.py", line 35, in <module>
    row = asyncio.get_event_loop().run_until_complete(go(make_engine(asynctest.CoroutineMock())))
  File "/usr/lib64/python3.6/asyncio/base_events.py", line 466, in run_until_complete
    return future.result()
  File "atest.py", line 27, in go
    async with engine.acquire() as conn:
AttributeError: __aexit__

Martiusweb · 2017-05-01T18:45:22Z

You must use MagicMock instead of CoroutineMock: Engine, _EngineAcquireContextManager, and _ConnectionContextManager are not coroutines.

Anyway, MagicMock is not smart enough to do what you want to achieve: you the mock system to infer the type of the result of engine.acquire() and conn.begin(), and it's not possible in pure Python. It would be the same problem with a non-asynchronous equivalent.

If you want to mock all the chain, you must do something like:

def make_engine():
    connection_mock = asynctest.MagicMock()
    connection_mock.begin.return_value = asynctest.MagicMock(
        aiopg.sa.connection._SAConnectionContextManager)

    acquire_mock = asynctest.MagicMock(
        aiopg.sa.engine._EngineAcquireContextManager)
    acquire_mock.__aenter__.return_value = connection_mock

    engine_mock = asynctest.MagicMock(aiopg.sa.engine.Engine)
    engine_mock.acquire.return_value = acquire_mock

    return asynctest.CoroutineMock(return_value=engine_mock)

Martiusweb · 2017-05-01T18:49:58Z

I implemented aenter, aexit, aiter and anext.

I think there are cases left to test, especially cases dealing with exceptions (eg: when an exception is raised inside an asynchronous context manager, the exception seems to be swallowed and lost).

It's also tedious to mock those magic methods, because the async context manager class must be used as mock spec. Classes like AsyncContextManagerMock and AsyncIteratorMock can be useful to provide a more user friendly API.

serg666 · 2017-05-02T16:03:48Z

@Martiusweb , thanks a lot!

The following code works fine

import asyncio
import aiopg.sa
import asynctest


def make_engine():
    connection_mock = asynctest.MagicMock(
        execute=asynctest.CoroutineMock(
            return_value=asynctest.CoroutineMock(
                fetchone=asynctest.CoroutineMock()
            )
        )
    )
    connection_mock.begin.return_value = asynctest.MagicMock(
        aiopg.sa.connection._SAConnectionContextManager)

    acquire_mock = asynctest.MagicMock(
        aiopg.sa.engine._EngineAcquireContextManager)
    acquire_mock.__aenter__.return_value = connection_mock

    engine_mock = asynctest.MagicMock(aiopg.sa.engine.Engine)
    engine_mock.acquire.return_value = acquire_mock

    return asynctest.CoroutineMock(return_value=engine_mock)

async def create_engine():
    kwargs = {'echo': True}
    return await aiopg.sa.create_engine(
        'dbname=dbname user=dbuser password=dbpasssword host=127.0.0.1',
        **kwargs
   )

async def go(get_engine):
    engine = await get_engine()
    async with engine.acquire() as conn:
        async with conn.begin():
            r = await conn.execute('SELECT version();')
    return await r.fetchone()


row = asyncio.get_event_loop().run_until_complete(go(create_engine))
print(row)

row = asyncio.get_event_loop().run_until_complete(go(make_engine()))
print(row)

the result is

python atest.py 
('PostgreSQL 9.6.2 on x86_64-suse-linux-gnu, compiled by gcc (SUSE Linux) 6.3.1 20170202 [gcc-6-branch revision 245119], 64-bit',)
<MagicMock name='mock.fetchone()' id='140316582692120'>
Unclosed connection
connection: <aiopg.connection.Connection object at 0x7f9e0014f470>

but on branch async_magic I have seen message about Unclosed connection when execute

row = asyncio.get_event_loop().run_until_complete(go(create_engine))

Note, on current version from pypi I have not seen this message.

Martiusweb · 2017-05-02T16:49:01Z

Hi,

This is likely because somewhere in your code an actual connection is created but never closed.
It might be left open because of the mock, but it's because of the way aiopg and/or your test crafted and it's not directly related to asynctest.

You'll have to track which part of your test uses real code rather than the mock.

serg666 · 2017-05-02T16:52:39Z

No no no!!!

the following code does not use MOCK at all

import asyncio
import aiopg.sa
import asynctest

'''
def make_engine():
    connection_mock = asynctest.MagicMock(
        execute=asynctest.CoroutineMock(
            return_value=asynctest.CoroutineMock(
                fetchone=asynctest.CoroutineMock()
            )
        )
    )
    connection_mock.begin.return_value = asynctest.MagicMock(
        aiopg.sa.connection._SAConnectionContextManager)

    acquire_mock = asynctest.MagicMock(
        aiopg.sa.engine._EngineAcquireContextManager)
    acquire_mock.__aenter__.return_value = connection_mock

    engine_mock = asynctest.MagicMock(aiopg.sa.engine.Engine)
    engine_mock.acquire.return_value = acquire_mock

    return asynctest.CoroutineMock(return_value=engine_mock)
'''

async def create_engine():
    kwargs = {'echo': True}
    return await aiopg.sa.create_engine(
        'dbname=db user=user password=passwd host=127.0.0.1',
        **kwargs
   )

async def go(get_engine):
    engine = await get_engine()
    async with engine.acquire() as conn:
        async with conn.begin():
            r = await conn.execute('SELECT version();')
    return await r.fetchone()


row = asyncio.get_event_loop().run_until_complete(go(create_engine))
print(row)

#row = asyncio.get_event_loop().run_until_complete(go(make_engine()))
#print(row)

and when I execute this code on current version from pypi everything is OK, but when I execute this code on the async_magic branch I have seen

('PostgreSQL 9.6.2 on x86_64-suse-linux-gnu, compiled by gcc (SUSE Linux) 6.3.1 20170202 [gcc-6-branch revision 245119], 64-bit',)
Unclosed connection
connection: <aiopg.connection.Connection object at 0x7fd9f28463c8>

serg666 · 2017-05-02T16:56:26Z

U can test it yourself. Just switch to current version from pypi and execute the code above. Then switch to async_magic branch and try to execute this code. U will see message about Unclosed connection

Martiusweb · 2017-05-02T17:00:59Z

In your example, you don't use asynctest at all. I don't see what I can do for you there.

Since it's not related to the async context managers mocking issue, if you think it's related to asynctest and can provide more details (for instance, use git bisect to find the commit which introduced a bug), please open a new issue.

serg666 · 2017-05-02T17:02:05Z

I just want to say, that on current version from pypi and on async_magic result of execution the above code is different. The only difference is asynctest version

serg666 · 2017-05-02T18:04:08Z

Executing the above code in both branches master and async_magic leads to message about Unclosed connection. But if I use current version from pypi https://pypi.python.org/pypi/asynctest/0.10.0 everything is ok

serg666 · 2017-05-02T18:12:58Z

If I switch to commit a3b7b5e on master (the current version in pypi) everything is OK. If I switch back to master I have got message about Unclosed connection

serg666 · 2017-05-02T18:22:00Z

Wow!

If I switch back to one commit from current master

git checkout HEAD~

everything is OK executing the code above. No message about Unclosed connection. If I switch to the HEAD again , I have got message about Unclosed connection. So, something wrong with commit e005798

This is about commit which introduced a bug (strange behavior).

serg666 · 2017-05-02T18:46:58Z

For reference: If I comment importing asynctest in the code above everything is OK on master (no message about Unclosed connection).

import asyncio
import aiopg.sa
# import asynctest
...

pfertyk · 2017-06-13T21:32:21Z

@Martiusweb what are the plans for this issue? Are __aenter__ and __aexit__ methods going to be supported by asynctest?

Martiusweb · 2017-06-19T08:23:08Z

Yes, I've been working on this but there are still some parts I need to fix before I can merge the PR:
#42

You can try the branch though, as the most common use cases are working.

thehesiod · 2017-09-22T01:27:00Z

nice work @Martiusweb on a real fix and @Galbar on work-around, this thread inspired us to do a simpler fix:

class MagicMockContext(MagicMock):
    def __init__(self, *args, **kwargs):
        super().__init__(*args, **kwargs)
        type(self).__aenter__ = CoroutineMock(return_value=MagicMock())
        type(self).__aexit__ = CoroutineMock(return_value=MagicMock())

with usage:

with asynctest.mock.patch('dummy.Dummy', new_callable=MagicMockContext) as mockClientSession:

argaen · 2017-10-16T18:58:36Z

@Martiusweb any chance the branch could be merged? I've been using it for a while and works for me. If not, what are the missing things? Maybe other people can help there.

Martiusweb · 2017-10-17T08:44:12Z

I'll review my work and list what's missing by the end of the week. Exception raised in the context manager are not propagated correctly yet: I need to write the tests to ensure it works.

I also would like to add an API which helps manipulating those mocks, but I'll probably do that in an other PR.

argaen · 2017-10-17T09:36:37Z

Cool, once the list is available I'll check if there is something I can help this. I prefer installing things from a released version rather than from specific branch/commit :P

Martiusweb · 2017-10-23T08:57:22Z

This issue has been fixed in the 0.11.0 release which has just been pushed to pypi.

Feedback is more than welcome! If you see anything buggy or that can be improved, open a new bug!

argaen · 2017-10-23T09:00:16Z

Good news, thanks a lot! :)

x0zzz · 2017-10-30T22:01:05Z

With asynctest==0.11.0 this should work, right?:

from asynctest import CoroutineMock
from asyncio import get_event_loop

async def f():
    async with CoroutineMock():
        print('f()')

get_event_loop().run_until_complete(f())

However I get:
AttributeError: __aexit__

Am I doing something wrong?

For completeness:

❯❯❯ pip freeze | ag asynctest                                                    async ✱
asynctest==0.11.0

Martiusweb · 2017-10-31T07:29:53Z

You must think of CoroutineMock as the mock of a coroutine function, nothing else. In your case, you should use MagicMock, not CoroutineMock.

(Note to self: I really need to work on the guide)

x0zzz · 2017-11-01T23:26:15Z

Sorry for being dense, but this:

from asynctest import MagicMock
from asyncio import get_event_loop

async def f():
    async with MagicMock():
        print('f()')

get_event_loop().run_until_complete(f())

gives this:
TypeError: object MagicMock can't be used in 'await' expression

Can you please help me?

Martiusweb · 2017-11-02T12:53:40Z

You spotted a bug: unless you specify a spec implementing __aenter__ and __aexit__, this will not work. I opened #55 and will work on it today if I can find the time.

Martiusweb · 2017-11-04T15:25:02Z

@x0zzz the bug is fixed in v0.11.1

x0zzz · 2017-11-04T21:55:42Z

Thank you so very much :)

thehesiod · 2017-11-13T21:19:04Z

btw just a q in case anyone knows off the top of their head, is there any quick way to ensure that __aenter__ __enter__ returns "self" by default (same magicmock)?

Martiusweb · 2017-11-14T09:39:54Z

Maybe I misunderstood your comment, but this is not the default behavior of unittest:

>>> mo = unittest.mock.MagicMock()
>>> with m as mm:
...   print(id(m), id(mm), m is mm)
... 
140366555841704 140366478933072 False

The simplest way to do this is to set the return_value:

mock = asynctest.mock.MagicMock()
mock.__aenter__.return_value = self

Martiusweb added the enhancement label Dec 20, 2016

This was referenced Jan 16, 2017

Support mocks of asynchronous context managers and asynchronous iterators #15

Closed

AttributeError: __aexit__ on asynctest.patch #33

Closed

Martiusweb self-assigned this Mar 9, 2017

Martiusweb closed this as completed Oct 23, 2017

thehesiod mentioned this issue May 3, 2018

AttributeError: __aexit__ when using wrapt.ObjectProxy on async context managers. GrahamDumpleton/wrapt#73

Open

MagicMock doesn't implement __aenter__ or __aexit__ #29

MagicMock doesn't implement __aenter__ or __aexit__ #29

Comments

txomon commented Dec 19, 2016

Martiusweb commented Dec 20, 2016

Gr1N commented Dec 20, 2016

txomon commented Dec 20, 2016

serg666 commented Jan 27, 2017

serg666 commented Jan 27, 2017 • edited Loading

Galbar commented Mar 21, 2017

Martiusweb commented Mar 28, 2017

serg666 commented Mar 30, 2017

Martiusweb commented Mar 30, 2017

serg666 commented Mar 30, 2017 • edited Loading

Martiusweb commented Mar 30, 2017

serg666 commented Mar 30, 2017 • edited Loading

Martiusweb commented Mar 30, 2017 • edited Loading

serg666 commented Apr 11, 2017 • edited Loading

Martiusweb commented May 1, 2017

Martiusweb commented May 1, 2017

serg666 commented May 2, 2017 • edited Loading

Martiusweb commented May 2, 2017

serg666 commented May 2, 2017 • edited Loading

serg666 commented May 2, 2017 • edited Loading

Martiusweb commented May 2, 2017

serg666 commented May 2, 2017 • edited Loading

serg666 commented May 2, 2017

serg666 commented May 2, 2017

serg666 commented May 2, 2017 • edited Loading

serg666 commented May 2, 2017 • edited Loading

pfertyk commented Jun 13, 2017

Martiusweb commented Jun 19, 2017

thehesiod commented Sep 22, 2017 • edited Loading

argaen commented Oct 16, 2017 • edited Loading

Martiusweb commented Oct 17, 2017

argaen commented Oct 17, 2017

Martiusweb commented Oct 23, 2017

argaen commented Oct 23, 2017

x0zzz commented Oct 30, 2017

Martiusweb commented Oct 31, 2017

x0zzz commented Nov 1, 2017

Martiusweb commented Nov 2, 2017 • edited Loading

Martiusweb commented Nov 4, 2017

x0zzz commented Nov 4, 2017

thehesiod commented Nov 13, 2017

Martiusweb commented Nov 14, 2017

MagicMock doesn't implement `aenter` or `aexit` #29

MagicMock doesn't implement `aenter` or `aexit` #29

serg666 commented Jan 27, 2017 •

edited

Loading

serg666 commented Mar 30, 2017 •

edited

Loading

serg666 commented Mar 30, 2017 •

edited

Loading

Martiusweb commented Mar 30, 2017 •

edited

Loading

serg666 commented Apr 11, 2017 •

edited

Loading

serg666 commented May 2, 2017 •

edited

Loading

serg666 commented May 2, 2017 •

edited

Loading

serg666 commented May 2, 2017 •

edited

Loading

serg666 commented May 2, 2017 •

edited

Loading

serg666 commented May 2, 2017 •

edited

Loading

serg666 commented May 2, 2017 •

edited

Loading

thehesiod commented Sep 22, 2017 •

edited

Loading

argaen commented Oct 16, 2017 •

edited

Loading

Martiusweb commented Nov 2, 2017 •

edited

Loading