Lets say I the following class;
class CompositionClass(object):
def __init__(self):
self._redis = Redis()
self._binance_client = BinanceClient()
def do_processing(self, data):
self._redis.write(data)
self._binance_client.buy(data.amount_to_buy)
# logic to actually unittest
return process_val
I have other objects which call external API as composition in my ComplexClass. When I am unittesting the logic of do_processing, I do not want to call these expensive API calls. I have checked throughly in SO and Google about unittesting; all examples are simple not that really useful. In my case how can I use unittest.mock to mock these objects?
One way of mocking the Redis and BinanceClient classes is to use the patch decorator in your test class, such as:
from unittest import TestCase
from unittest.mock import patch
from package.module import CompositionClass
class TestCompositionClass(TestCase):
#patch('package.module.BinanceClient')
#patch('package.module.Redis')
def test_do_processing(self, mock_redis, mock_binance):
c = CompositionClass()
data = [...]
c.do_processing(data)
# Perform your assertions
# Check that mocks were called
mock_redis.return_value.write.assert_called_once_with(data)
mock_binance.return_value.buy.assert_called_once_with(data.amount_to_buy)
Note that the path specified to #patch is the path to module containing the CompositionClass and its imports for Redis and BinanceClient. The patching happens in that module, not the module containing the Redis and BinanceClient implementations themselves.
You need to set a value that must be returned by your API call, to this function:
from unittest.mock import MagicMock
class Tester(unittest.TestCase):
def setUp(self):
pass
def test_do_processing(self):
self.API_function = MagicMock(return_value='API_response')
# test logic
Related
How it started
I'm testing a class, ClassToTest, that makes API calls using atlassian-python-api. The tests are going to ensure that ClassToTest performs correctly with the data it gets back from the API. Many of the atlassian-python-api API calls use instantiated classes which inherit from the same base class or group of top-level classes.
I'd like to write tests that will expose breaks in the API contract if the wrong data is returned or API calls fail, while also testing the class I wrote to ensure it does the correct things with the data returned from the API. In order to do this, I was hoping to use unittest.mock.patch("path.to.Comment", autospec=True) to copy the API spec into the MagicMock, but I don't believe it's working properly.
For the purposes of the question, ClassToTest is not that important; what I am aiming to solve is how to setup and configure the pytest fixtures in a way that I can use them to mimic the API endpoints that will return the data that ClassToTest will act upon. Ideally I'd like to reuse the fixtures without having patch conflicts. I've included relevant code from ClassToTest for illustrative purposes here:
class_to_test.py:
from atlassian.bitbucket import Cloud
from typing import NamedTuple
# these are hardcoded constants that work with the production API
from src.constants import (
PULL_REQUEST_ID,
REPOSITORY,
WORKSPACE,
)
CommentType = NamedTuple("CommentType", [("top_level", str), ("inline", str)])
class ClassToTest:
def _get_token(self):
"""this returns a token of type(str)"""
def __init__(self, workspace, repository, pull_request_id):
self.active_comments = None
self.environment = sys.argv[1]
self.comment_text = CommentType(
top_level=r"top_level_comment text", inline=r"inline_comment text"
)
self.cloud = Cloud(token=self._get_token(), cloud=True)
self.workspace = self.cloud.workspaces.get(workspace)
self.repository = self.cloud.repositories.get(workspace, repository)
self.pull_request = self.repository.pullrequests.get(id=pull_request_id)
def _get_active_comments(self):
"""Returns a list of active (non-deleted) comments"""
return [
c for c in self.pull_request.comments() if c.data["deleted"] is False
]
# a few more methods here
def main():
instance = ClassToTest(WORKSPACE, REPOSITORY, PULL_REQUEST_ID)
# result = instance.method() for each method I need to call.
# do things with each result
if __name__ == "__main__":
main()
The class has methods that retrieve comments from the API (_get_active_comments, above), act on the retrieved comments, retrieve pull requests, and so on. What I am trying to test is that the class methods act correctly on the data received from the API, so I need to accurately mock data returned from API calls.
How it's going
I started with a unittest.Testcase style test class and wanted the flexibility of pytest fixtures (and autospec), but removed Testcase entirely when I discovered that pytest fixtures don't really work with it. I'm currently using a pytest class and conftest.py as follows:
/test/test_class_to_test.py:
import pytest
from unittest.mock import patch
from src.class_to_test import ClassToTest
#pytest.mark.usefixtures("mocked_comment", "mocked_user")
class TestClassToTest:
# We mock Cloud here as ClassToTest calls it in __init__ to authenticate with the API
# _get_token retrieves an access token for the API; since we don't need it, we can mock it
#patch("src.test_class_to_test.Cloud", autospec=True)
#patch.object(ClassToTest, "_get_token").
def setup_method(self, method, mock_get_token, mock_cloud):
mock_get_token.return_value = "token"
self.checker = ClassToTest("WORKSPACE", "REPOSITORY", 1)
def teardown_method(self, method):
pass
def test_has_top_level_and_inline_comments(self, mocked_comment, mocked_pull_request):
mock_top_comment = mocked_comment(raw="some text to search for later")
assert isinstance(mock_top_comment.data, dict)
assert mock_top_comment.data["raw"] == "some text to search for later"
# the assert below this line is failing
assert mock_top_comment.user.account_id == 1234
conftest.py:
import pytest
from unittest.mock import patch, PropertyMock
from atlassian.bitbucket.cloud.common.comments import Comment
from atlassian.bitbucket.cloud.common.users import User
#pytest.fixture()
def mocked_user(request):
def _mocked_user(account_id=1234):
user_patcher = patch(
f"atlassian.bitbucket.cloud.common.users.User", spec_set=True, autospec=True
)
MockUser = user_patcher.start()
data = {"type": "user", "account_id": account_id}
url = "user_url"
user = MockUser(data=data, url=url)
# setup mocked properties
mock_id = PropertyMock(return_value=account_id)
type(user).id = mock_id
mockdata = PropertyMock(return_value=data)
type(user).data = mockdata
request.addfinalizer(user_patcher.stop)
return user
return _mocked_user
#pytest.fixture()
def mocked_comment(request, mocked_user):
def _mocked_comment(raw="", inline=None, deleted=False, user_id=1234):
comment_patcher = patch(
f"atlassian.bitbucket.cloud.common.comments.Comment", spec_set=True, autospec=True
)
MockComment = comment_patcher.start()
data = {
"type": "pullrequest_comment",
"user": mocked_user(user_id),
"raw": raw,
"deleted": deleted,
}
if inline:
data["inline"] = {"from": None, "to": 1, "path": "src/code_issues.py"}
data["raw"] = "this is an inline comment"
comment = MockComment(data)
# setup mocked properties
mockdata = PropertyMock(return_value=data)
type(comment).data = mockdata
# mockuser = PropertyMock(return_value=mocked_user(user_id))
# type(comment).user = mockuser
request.addfinalizer(comment_patcher.stop)
return comment
return _mocked_comment
The problem I am encountering is that the assert mock_top_comment.user.account_id == 1234 line fails when running the test, with the following error:
> assert mock_top_comment.user.account_id == 1234
E AssertionError: assert <MagicMock name='Comment().user.account_id' id='4399290192'> == 1234
E + where <MagicMock name='Comment().user.account_id' id='4399290192'> = <MagicMock name='Comment().user' id='4399634736'>.account_id
E + where <MagicMock name='Comment().user' id='4399634736'> = <NonCallableMagicMock name='Comment()' spec_set='Comment' id='4399234928'>.user
How do I get the mock User class to attach to the mock Comment class in the same way that the real API makes it work? Is there something about autospec that I'm missing, or should I be abandoning unittest.mock.patch entirely and using something else?
Extra credit (EDIT: in retrospect, this may be the most important part)
I'm using mocked_comment as a pytest fixture factory and want to reuse it multiple times in the same test (for example to create multiple mocked Comments returned in a list). So far, each time I've tried to do that, I've been met with the following error:
def test_has_top_level_and_inline_comments(self, mocked_comment, mocked_pull_request):
mock_top_comment = mocked_comment(raw="Some comment text")
> mock_inline_comment = mocked_comment(inline=True)
...
test/conftest.py:30: in _mocked_comment
MockComment = comment_patcher.start()
/opt/homebrew/Cellar/python#3.10/3.10.8/Frameworks/Python.framework/Versions/3.10/lib/python3.10/unittest/mock.py:1585: in start
result = self.__enter__()
...
> raise InvalidSpecError(
f'Cannot autospec attr {self.attribute!r} from target '
f'{target_name!r} as it has already been mocked out. '
f'[target={self.target!r}, attr={autospec!r}]')
E unittest.mock.InvalidSpecError: Cannot autospec attr 'Comment' from target 'atlassian.bitbucket.cloud.common.comments' as it has already been mocked out. [target=<module 'atlassian.bitbucket.cloud.common.comments' from '/opt/homebrew/lib/python3.10/site-packages/atlassian/bitbucket/cloud/common/comments.py'>, attr=<MagicMock name='Comment' spec_set='Comment' id='4398964912'>]
I thought the whole point of a pytest fixture factory was to be reusable, but I believe that using an autospec mock complicates things quite a bit. I don't want to have to hand copy every detail from the API spec into the tests, as that will have to be changed if anything in the API changes. Is there a solution for this that involves automatically and dynamically creating the necessary classes in the mocked API with the correct return values for properties?
One thing I'm considering is separating the testing into two parts: API contract, and ClassToTest testing. In this way I can write the tests for ClassToTest without relying on the API and they will pass as long as I manipulate the received data correctly. Any changes to the API will get caught by the separate contract testing tests. Then I can use non-factory fixtures with static data for testing ClassToTest.
For now though, I'm out of ideas on how to proceed with this. What should I do here? Probably the most important thing to address is how to properly link the User instance with the Comment instance in the fixtures so that my method calls in test work the same way as they do in production. Bonus points if we can figure out how to dynamically patch multiple fixtures in a single test.
I've started looking at this answer, but given the number of interconnected classes and properties, I'm not sure it will work without writing out a ton of fixtures. After following the directions and applying them to the User mock inside the Comment mock, I started getting the error in the Extra Credit section above, where autospec couldn't be used as it has already been mocked out.
I have a python file (a.py) which defines a function, and a class which uses it as a default parameter in it's init method and initializes another imported class. This is my a.py
import OtherClass
def useful_default_func():
//do something useful
class MyClass(object):
def __init__(self, def_func=useful_default_func):
self.other_class = OtherClass(def_func())
//do something useful
I am trying to mock the useful_default_func in my test file.
class TestMyClass(unittest.TestCase):
#patch('a.useful_default_func')
#patch('a.OtherClass')
test_init(self, mock_other_class, mock_default_func):
myc= MyClass()
mock_other_class.assert_called_once_with(mock_default_func)
// further tests
However, the mock_default_func is not patching and my test fails saying,
Expected: OtherClass(<MagicMock id='xxx'>)
Actual: OtherClass(<function useful_default_func at 0x7f155858b378>)
Fairly new to the python mock lib, so not really sure, what is happening here or what I am doing wrong or how should I be approaching it?
Something like this could work:
def mocked_fct():
return 42
class TestMyClass(unittest.TestCase):
#mock.patch.object(a.MyClass.__init__, '__defaults__', (mocked_fct,))
#patch('a.OtherClass')
def test_init(self, mock_other_class):
myc = MyClass()
mock_other_class.assert_called_once_with(mocked_fct)
I didn't use a mock for the mocked default function here, this can be changed if needed. The main point is that you can mock the function defaults.
Note: this assumes that you call
self.other_class = OtherClass(def_func)
instead of
self.other_class = OtherClass(def_func())
If this was not a typo, your assertion would not be correct. In this case, you could instead use:
mock_other_class.assert_called_once_with(mocked_fct())
mock_other_class.assert_called_once_with(42) # same as above
I want to access the calling environment from an imported module.
import child
…
def test(xxx):
print("This is test " + str(xxx))
child.main()
…
now on child:
import inspect
def main():
caller = inspect.currentframe().f_back
caller.f_globals['test']("This is my test")
This works, but it's not fancy. Is there a simplification like 'self' when use in a class? the idea is to do: caller.test('abc') instead.
One option to pass the caller as a parameter like: child.main(self), however self is not available in this context.
Python only load one version of a module so, tempted with this idea:
import sys
myself=sys.modules[__name__]
a then sending myself to the child:
…
child.main(myself)
…
Creates a reference to (a new) module, but not the running one, this is like creating a new class: one code buy a different environment.
If you already have a way of accessing the correct functions and data that works, why not just store f_globals on an instance of a wrapper class and then call things from the instance as if they were unbound properties? You could use the class itself, but using an instance ensures that the data you get from the imported file are valid when you create the object. Then you can access using the dot operator the way you want. This is your child file:
import inspect
class ImportFile:
def __init__(self, members):
self.__dict__.update(members)
def main():
caller = inspect.currentframe().f_back
imported_file = ImportFile(caller.f_globals)
imported_file.test("This is my test")
Outputs:
This is test This is my test
Admittedly, I don't have your setup, importantly the module you're trying to pull from, so it's hard to confirm whether or not this will work for you even though it has for me, but I think you could also use your method of calling main with globals() or even inspect.getmembers() since while inside the module you're importing you're still on the frame you're accessing with f_back from inside child.
The imported module:
import child
def test(xxx):
print("This is test " + str(xxx))
child.main(globals())
Child:
import inspect
class ImportFile:
def __init__(self, members):
self.__dict__.update(members)
def main(caller):
imported_file = ImportFile(caller)
imported_file.test("This is my test")
Outputs:
This is test This is my test
I want to unit test some code that calls a method of the boto3 s3 client.
I can't use moto because this particular method (put_bucket_lifecycle_configuration) is not yet implemented in moto.
I want to mock the S3 client and assure that this method was called with specific parameters.
The code I want to test looks something like this:
# sut.py
import boto3
class S3Bucket(object):
def __init__(self, name, lifecycle_config):
self.name = name
self.lifecycle_config = lifecycle_config
def create(self):
client = boto3.client("s3")
client.create_bucket(Bucket=self.name)
rules = # some code that computes rules from self.lifecycle_config
# I want to test that `rules` is correct in the following call:
client.put_bucket_lifecycle_configuration(Bucket=self.name, \
LifecycleConfiguration={"Rules": rules})
def create_a_bucket(name):
lifecycle_policy = # a dict with a bunch of key/value pairs
bucket = S3Bucket(name, lifecycle_policy)
bucket.create()
return bucket
In my test, I'd like to call create_a_bucket() (though instantiating an S3Bucket directly is also an option) and make sure that the call to put_bucket_lifecycle_configuration was made with the correct parameters.
I have messed around with unittest.mock and botocore.stub.Stubber but have not managed to crack this. Unless otherwise urged, I am not posting my attempts since they have not been successful so far.
I am open to suggestions on restructuring the code I'm trying to test in order to make it easier to test.
Got the test to work with the following, where ... is the remainder of the arguments that are expected to be passed to s3.put_bucket_lifecycle_configuration().
# test.py
from unittest.mock import patch
import unittest
import sut
class MyTestCase(unittest.TestCase):
#patch("sut.boto3")
def test_lifecycle_config(self, cli):
s3 = cli.client.return_value
sut.create_a_bucket("foo")
s3.put_bucket_lifecycle_configuration.assert_called_once_with(Bucket="foo", ...)
if __name__ == '__main__':
unittest.main()
I want to mock a method of a class and use wraps, so that it is actually called, but I can inspect the arguments passed to it. I have seen at several places (here for example) that the usual way to do that is as follows (adapted to show my point):
from unittest import TestCase
from unittest.mock import patch
class Potato(object):
def foo(self, n):
return self.bar(n)
def bar(self, n):
return n + 2
class PotatoTest(TestCase):
spud = Potato()
#patch.object(Potato, 'foo', wraps=spud.foo)
def test_something(self, mock):
forty_two = self.spud.foo(n=40)
mock.assert_called_once_with(n=40)
self.assertEqual(forty_two, 42)
However, this instantiates the class Potato, in order to bind the mock to the instance method spud.foo.
What I need is to mock the method foo in all instances of Potato, and wrap them around the original methods. I.e, I need the following:
from unittest import TestCase
from unittest.mock import patch
class Potato(object):
def foo(self, n):
return self.bar(n)
def bar(self, n):
return n + 2
class PotatoTest(TestCase):
#patch.object(Potato, 'foo', wraps=Potato.foo)
def test_something(self, mock):
self.spud = Potato()
forty_two = self.spud.foo(n=40)
mock.assert_called_once_with(n=40)
self.assertEqual(forty_two, 42)
This of course doesn't work. I get the error:
TypeError: foo() missing 1 required positional argument: 'self'
It works however if wraps is not used, so the problem is not in the mock itself, but in the way it calls the wrapped function. For example, this works (but of course I had to "fake" the returned value, because now Potato.foo is never actually run):
from unittest import TestCase
from unittest.mock import patch
class Potato(object):
def foo(self, n):
return self.bar(n)
def bar(self, n):
return n + 2
class PotatoTest(TestCase):
#patch.object(Potato, 'foo', return_value=42)#, wraps=Potato.foo)
def test_something(self, mock):
self.spud = Potato()
forty_two = self.spud.foo(n=40)
mock.assert_called_once_with(n=40)
self.assertEqual(forty_two, 42)
This works, but it does not run the original function, which I need to run because the return value is used elsewhere (and I cannot fake it from the test).
Can it be done?
Note The actual reason behind my needs is that I'm testing a rest api with webtest. From the tests I perform some wsgi requests to some paths, and my framework instantiates some classes and uses their methods to fulfill the request. I want to capture the parameters sent to those methods to do some asserts about them in my tests.
In short, you can't do this using Mock instances alone.
patch.object creates Mock's for the specified instance (Potato), i.e. it replaces Potato.foo with a single Mock the moment it is called. Therefore, there is no way to pass instances to the Mock as the mock is created before any instances are. To my knowledge getting instance information to the Mock at runtime is also very difficult.
To illustrate:
from unittest.mock import MagicMock
class MyMock(MagicMock):
def __init__(self, *a, **kw):
super(MyMock, self).__init__(*a, **kw)
print('Created Mock instance a={}, kw={}'.format(a,kw))
with patch.object(Potato, 'foo', new_callable=MyMock, wrap=Potato.foo):
print('no instances created')
spud = Potato()
print('instance created')
The output is:
Created Mock instance a=(), kw={'name': 'foo', 'wrap': <function Potato.foo at 0x7f5d9bfddea0>}
no instances created
instance created
I would suggest monkey-patching your class in order to add the Mock to the correct location.
from unittest.mock import MagicMock
class PotatoTest(TestCase):
def test_something(self):
old_foo = Potato.foo
try:
mock = MagicMock(wraps=Potato.foo, return_value=42)
Potato.foo = lambda *a,**kw: mock(*a, **kw)
self.spud = Potato()
forty_two = self.spud.foo(n=40)
mock.assert_called_once_with(self.spud, n=40) # Now needs self instance
self.assertEqual(forty_two, 42)
finally:
Potato.foo = old_foo
Note that you using called_with is problematic as you are calling your functions with an instance.
Do you control creation of Potato instances, or at least have access to these instances after creating them? You should, else you'd not be able to check particular arg lists.
If so, you can wrap methods of individual instances using
spud = dig_out_a_potato()
with mock.patch.object(spud, "foo", wraps=spud.foo) as mock_spud:
# do your thing.
mock_spud.assert_called...
Your question looks identical to python mock - patching a method without obstructing implementation to me. https://stackoverflow.com/a/72446739/9230828 implements what you want (except that it uses a with statement instead of a decorator). wrap_object.py:
# Copyright (C) 2022, Benjamin Drung <bdrung#posteo.de>
#
# Permission to use, copy, modify, and/or distribute this software for any
# purpose with or without fee is hereby granted, provided that the above
# copyright notice and this permission notice appear in all copies.
#
# THE SOFTWARE IS PROVIDED "AS IS" AND THE AUTHOR DISCLAIMS ALL WARRANTIES
# WITH REGARD TO THIS SOFTWARE INCLUDING ALL IMPLIED WARRANTIES OF
# MERCHANTABILITY AND FITNESS. IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR
# ANY SPECIAL, DIRECT, INDIRECT, OR CONSEQUENTIAL DAMAGES OR ANY DAMAGES
# WHATSOEVER RESULTING FROM LOSS OF USE, DATA OR PROFITS, WHETHER IN AN
# ACTION OF CONTRACT, NEGLIGENCE OR OTHER TORTIOUS ACTION, ARISING OUT OF
# OR IN CONNECTION WITH THE USE OR PERFORMANCE OF THIS SOFTWARE.
import contextlib
import typing
import unittest.mock
#contextlib.contextmanager
def wrap_object(
target: object, attribute: str
) -> typing.Generator[unittest.mock.MagicMock, None, None]:
"""Wrap the named member on an object with a mock object.
wrap_object() can be used as a context manager. Inside the
body of the with statement, the attribute of the target is
wrapped with a :class:`unittest.mock.MagicMock` object. When
the with statement exits the patch is undone.
The instance argument 'self' of the wrapped attribute is
intentionally not logged in the MagicMock call. Therefore
wrap_object() can be used to check all calls to the object,
but not differentiate between different instances.
"""
mock = unittest.mock.MagicMock()
real_attribute = getattr(target, attribute)
def mocked_attribute(self, *args, **kwargs):
mock.__call__(*args, **kwargs)
return real_attribute(self, *args, **kwargs)
with unittest.mock.patch.object(target, attribute, mocked_attribute):
yield mock
Then you can write following unit test:
from unittest import TestCase
from wrap_object import wrap_object
class Potato:
def foo(self, n):
return self.bar(n)
def bar(self, n):
return n + 2
class PotatoTest(TestCase):
def test_something(self):
with wrap_object(Potato, 'foo') as mock:
self.spud = Potato()
forty_two = self.spud.foo(n=40)
mock.assert_called_once_with(n=40)
self.assertEqual(forty_two, 42)