Revamped api.py (with test and 100% coverage)

api.py

"""
Slack Web API
=============

The `Slack Web API`_ let you communicate with Slack.

Usage:
------

The following example calls the ``api.test`` method which test whether your
token is valid.

.. code-block:: python

    import os
    import asyncio

    from votebot.api import call


    token = os.environ['SLACK_TOKEN']
    loop = asyncio.get_event_loop()
    response = loop.run_until_complete(call('api.test',
                                            token=token))
    print(response)
    loop.close()



.. _Slack Web API: https://api.slack.com/web/

"""

import json
from collections.abc import Mapping

from aiohttp import ClientSession, FormData


async def call(method, file=None, **kwargs):
    """
    Perform an API call to Slack.

    :param file: File pointer
    :type file: file

    :Keyword Arguments:
        All the arguments required by the Slack API.

    :return: JSON response.
    :rtype: dict
    """
    # JSON encode any sub-structure...
    for k, w in kwargs.items():
        # list, tuple or dict but not a str.
        if isinstance(w, (Mapping, list, tuple)):
            kwargs[k] = json.dumps(w)

    form = FormData(kwargs)

    # Handle file upload
    if file:
        form.add_field('file', file)

    with ClientSession() as session:
        async with session.post('https://slack.com/api/{0}'.format(method),
                                data=form) as response:
            assert 200 == response.status, response
            return await response.json()

test_api.py

from urllib.parse import urlencode

import pytest

from asynctest import patch
from votebot.api import call


@pytest.fixture(scope='session')
def hello_file(tmpdir_factory):
    fn = tmpdir_factory.mktemp('data').join('hello.txt')
    fn.write('Hello world!\n')
    return str(fn)


class MockClientSession:
    def __enter__(self):
        return MockSession()

    def __exit__(self, *args):
        pass


class MockSession:
    def post(self, *args, **kwargs):
        return MockRequest(*args, **kwargs)


class MockRequest:
    def __init__(self, *args, **kwargs):
        self.args = args
        self.kwargs = kwargs

    async def __aenter__(self):
        return MockResponse(200, *self.args, **self.kwargs)

    async def __aexit__(self, *args):
        pass


class MockResponse:
    def __init__(self, status, *args, **kwargs):
        self.status = status
        self.args = args
        self.kwargs = kwargs

    async def json(self):
        return {'ok': False,
                'error': 'I am a mock',
                'args': self.args,
                'kwargs': self.kwargs}


@pytest.mark.asyncio
async def test_api_simple():
    with patch('votebot.api.ClientSession', new=MockClientSession):
        response = await call('api.test', token='xoxb-123')

    assert not response['ok']
    assert 'I am a mock' == response['error']
    assert ('https://slack.com/api/api.test',) == response['args']

    data = response['kwargs']['data']('utf-8')
    assert b'token=xoxb-123' == data


@pytest.mark.asyncio
async def test_api_subfields():
    with patch('votebot.api.ClientSession', new=MockClientSession):
        response = await call('api.dummy', fields=[1, 2, 3])

    data = response['kwargs']['data']('utf-8')
    assert urlencode({'fields': '[1, 2, 3]'}).encode('utf-8') == data


@pytest.mark.asyncio
async def test_api_file(hello_file):
    with patch('votebot.api.ClientSession', new=MockClientSession):
        with open(hello_file, 'r', encoding='utf-8') as f:
            response = await call('api.file', file=f)

    data = response['kwargs']['data']
    assert data.is_multipart