This is my sample code:
from path.lib import DBInterface
class MyClass:
def __init__(self):
self.something = "something"
def _my_method(self, some_key, new_setup):
with DBInterface(self.something) as ic:
current_setup = ic.get(some_key)
if current_setup != new_setup:
with DBInterface(self.something) as ic:
ic.set(new_setup)
def public_method(self, some_key, new_setup):
return self._my_method(some_key, new_setup)
(my actual code is bit more complex, but i cant put it here on public :)
Now, what I want to do is, I want to completely mock the imported class DBInterface, because I do not want my unittests to do anything in DB.
BUT I also need the ic.get(some_key) to return some value, or to be more precise, I need to set the value it returns, because thats the point of my unittests, to test if the method behave properly according to value returned from DB.
This is how far I got:
class TestMyClass:
def test_extractor_register(self, mocker):
fake_db = mocker.patch.object('my_path.my_lib.DBInterface')
fake_db.get.return_value = None
# spy_obj = mocker.spy(MyClass, "_my_method")
test_class = MyClass()
# Test new registration in _extractor_register
result = test_class.public_method(Tconf.test_key, Tconf.test_key_setup)
fake_db.assert_has_calls([call().__enter__().get(Tconf.test_key),
call().__enter__().set(Tconf.test_key, Tconf.test_key_setup)])
# spy_obj.assert_called_with(ANY, Tconf.test_key, Tconf.test_key_setup)
assert result.result_status.status_code == Tconf.status_ok.status_code
assert result.result_data == MyMethodResult.new_reg
But i am unable to set return value for call().__enter__().get(Tconf.test_key).
I have been trying many approaches:
fake_db.get.return_value = None
fake_db.__enter__().get.return_value = None
fake_db.__enter__.get = Mock(return_value=None)
mocker.patch.object(MyClass.DBInterface, "get").return_value = None
None of that is actually working and I am running out of options I can think about.
Without having more code or errors that are being produced, it's tough to provide a conclusive answer.
However, if you truly only need to specify a return value for set() I would recommend using MagicMock by virtue of patch --
from unittest.mock import patch
#patch("<MyClassFile>.DBInterface", autospec=True)
def test_extractor_register(mock_db):
mock_db.set.return_value = "some key"
# Rest of test code
I have a class that have a variable in __init__ and a method. The variable stores a string value that represents the s3 bucket name, which will be used by the method.
class Manage:
def __init__(self):
self.bucket = 'doc'
def read_file(self):
bucket = self.bucket
...
return file
And I am writing a test case to test the method but the problem is I want to use a different bucket, so I want to patch the value of that variable.
Code I tried
import Manage
def test_manage(monkeypath):
monkeypath.setattr(Manage, 'bucket', 'doc2')
...
The above code is not working, since the bucket is not a class-level variable (i guess). I don't know how should I change that
As #gold_cy suggested, you can set it after instantiating the object:
import Manage
def test_manage():
manage = Manage()
manage.bucket = 'doc2'
...
I want to know how can check if the boto3 client object already instantiated or not. i have below code for creating the object for aws dynamodb
import boto3
def aws_dynamodb():
return boto3.resource("dynamodb")
def get_db_con():
dynamo_conn=aws_dynamodb()
return dynamo_conn
Now the above 'get_db_con()' return the connection to the dynamodb. but i want to make sure that 'get_db_con' not creating the client object from the 'aws_dynamodb()' everytime when its been called.
for eg:
def aws_db_table(table):
con=get_db_con()
return con.table(table)
account_table=aws_db_table("my_ac_table")
audit_table=aws_db_table("audit_table")
so here whenever i call the 'aws_db_table', it should not create the client for 'aws_dynamodb()' for everytime.
so how i can check it if the aws_dynamodb() is already instantiated or not creating new client object. Because creating client object everytime is costly..
Note: I want to run the code in Lambda function
Please help us on this..
Thanks
I usually go with a low-tech solution with a global variable that looks something like this:
import boto3
# Underscore-prefix to indicate this is something private
_TABLE_RESOURCE = None
def get_table_resource():
global _TABLE_RESOURCE
if _TABLE_RESOURCE is None:
_TABLE_RESOURCE = boto3.resource("dynamodb").Table("my_table")
return _TABLE_RESOURCE
def handler(event, context):
table = get_table_resource()
# ...
Global variables are persisted across Lambda executions, that's why this works.
Another option would be to use the lru_cache from functools, which uses memoization.
from functools import lru_cache
import boto3
#lru_cache(maxsize=128)
def get_table_resource():
return boto3.resource("dynamodb").Table("my_table")
def handler(event, context):
table = get_table_resource()
# ...
For those not familiar with memoization the first solution is probably easier to read + understand.
(Note: I wrote the code from memory, there may be bugs)
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)