I have a python function with a lot of functionality and several inner functions. I want to mock out the return value of one of those functions. Is it possible to use the mock package to mock out the inner function?
Here's an example
def outer(values):
a = 1
def inner():
return np.mean(values)
if inner() == 1:
return None
return inner()
Ok it's a strange example, but what I want is to mock out inner() to return a certain value. I tried to mock with #mock.patch('outer.inner') and I tried #mock.patch.object(outer, 'inner'), but neither works. Is it possible to mock a closure?
As far as I've found so far the answer is "you can't". Disappointing, but actionable.
In my case I was able to mock out some other call such that the closure returned what I wanted. In the example above it would be like
def test_outer_mean_1(self):
with mock.patch('np.mean', return_value=1):
self.assertIsNone(outer(None))
def test_outer_mean_not_1(self):
with mock.patch('np.mean', return_value=2):
self.assertEqual(2, outer(None))
If anybody comes up with a better answer, I'd be eager to hear it.
related question Mocking a local variable of a function in python
Disclaimer: I'm not saying this is the right approach, mocking np.mean is much better.
I have come up with a workaround: the idea is to change the code of the function at run time and execute the new function.
Here is the code:
from _pytest._code import Code
def convert_function_in_function(func):
context = getattr(func, "__globals__", {})
code = Code.from_function(func)
source = code.source()
new_body = ["from unittest import mock", "new_mock = mock.MagicMock()"] + source.lines[0:2] + [
" inner=new_mock"] + source.lines[4:]
compiled = compile("\n".join(new_body), str(code.path), "exec")
exec(compiled, context)
return context['outer'], context['new_mock']
def test_outer_mean_specific_value():
new_outer, mock_inner = convert_function_in_function(outer)
mock_inner.return_value = 2
assert 2 == new_outer(5)
Explanation: convert_function_in_function makes the code to be
from unittest import mock
new_mock = mock.MagicMock()
def outer(values):
a = 1
inner=new_mock
if inner() == 1:
return None
return inner()
Then it returns the new function and the matching mock. You can then change the mock behaviour and call the new function.
Related
I want to be able to mock a function that mutates an argument, and that it's mutation is relevant in order for the code to continue executing correctly.
Consider the following code:
def mutate_my_dict(mutable_dict):
if os.path.exists("a.txt"):
mutable_dict["new_key"] = "new_value"
return True
def function_under_test():
my_dict = {"key": "value"}
if mutate_my_dict(my_dict):
return my_dict["new_key"]
return "No Key"
def test_function_under_test():
with patch("stack_over_flow.mutate_my_dict") as mutate_my_dict_mock:
mutate_my_dict_mock.return_value = True
result = function_under_test()
assert result == "new_value"
**Please understand i know i can just mock os.path.exists in this case but this is just an example. I intentionally want to mock the function and not the external module.
**
I also read the docs here:
https://docs.python.org/3/library/unittest.mock-examples.html#coping-with-mutable-arguments
But it doesn't seem to fit in my case.
This is the test i've written so far, but it obviously doesn't work since the key changes:
def test_function_under_test():
with patch("stack_over_flow.mutate_my_dict") as mutate_my_dict_mock:
mutate_my_dict_mock.return_value = True
result = function_under_test()
assert result == "new_value"
Thanks in advance for all of your time :)
With the help of Peter i managed to come up with this final test:
def mock_mutate_my_dict(my_dict):
my_dict["new_key"] = "new_value"
return True
def test_function_under_test():
with patch("stack_over_flow.mutate_my_dict") as mutate_my_dict_mock:
mutate_my_dict_mock.side_effect = mock_mutate_my_dict
result = function_under_test()
assert result == "new_value"
How it works is that with a side effect you can run a function instead of the intended function.
In this function you need to both change all of the mutating arguments and return the value returned.
I am adding testing to a pipeline project, code is already written and in production so it cannot be changed to accommodate the tests.
In simplest terms, if I have a function like so:
def other_foo():
return 1
def foo():
res = other_foo()
return res
In practicality, the other_foo call will return a variety of responses, but for testing, I want to create a fixed response to test foo.
So in my test I want to create a fixed response to other_foo of 2. and my test evaluation to be something like:
def test_foo():
# some mocking or nesting handle here for other_foo
res = foo()
assert res == 2
Use the patch decorator from unitest.mock and patch your module local variable.
from your.module import foo
from unitest.mock import patch
#patch('your.module.other_foo')
def test_foo(mock_other_foo):
mock_other_foo.return_value = 3
assert foo() == 3
mock_other_foo.return_value = 42
assert foo() == 42
You can find more information here and there.
i am new to python unit testing. Want to mock a function that calls other functions.
Here is my function that i want to mock
def has_groups(self, group_names):
auth_user_id = AuthUser.get_by_email(self.userEmail).id
auth_user_groups = AuthUserGroups.get_group_by_user_id(auth_user_id)
for auth_user_group in auth_user_groups:
if auth_user_group.group.name in group_names:
return True
return False
has_groups should return True only when it get's 'Admin' as parameter.
Here is my test
def my_test(self):
uid = self.auth_user.get_by_email = Mock(return_value=73)
groups = AuthUserGroups.get_group_by_user_id = Mock(uid, return_value='Admin')
self.auth_user.has_groups = Mock(groups, return_value=True)
but it's not working fine. I will appreciate if anyone help me
Can i use patch decorator for this and how?
As I understand your has_groups function is method. I think it's better to mock whole class or independent function. On this situation you could mock AuthUserGroups, method return value and patch module with has_groups method implementation. So you'll have test like this:
from unittest import mock
def my_test(self):
group = mock.MagicMock()
group.group.name = 'Admin'
fake_auth_user_groups = mock.MagicMock()
fake_auth_user_groups.get_group_by_user_id.return_value = [group]
with mock.patch('your_module.AuthUserGroups', fake_auth_user_groups):
self.auth_user.has_groups(['Admin'])
Basically I want to do something like this:
How can I hook a function in a python module?
but I want to call the old function after my own code.
like
import whatever
oldfunc = whatever.this_is_a_function
def this_is_a_function(parameter):
#my own code here
# and call original function back
oldfunc(parameter)
whatever.this_is_a_function = this_is_a_function
Is this possible?
I tried copy.copy, copy.deepcopy original function but it didn't work.
Something like this? It avoids using globals, which is generally a good thing.
import whatever
import functools
def prefix_function(function, prefunction):
#functools.wraps(function)
def run(*args, **kwargs):
prefunction(*args, **kwargs)
return function(*args, **kwargs)
return run
def this_is_a_function(parameter):
pass # Your own code here that will be run before
whatever.this_is_a_function = prefix_function(
whatever.this_is_a_function, this_is_a_function)
prefix_function is a function that takes two functions: function and prefunction. It returns a function that takes any parameters, and calls prefunction followed by function with the same parameters. The prefix_function function works for any callable, so you only need to program the prefixing code once for any other hooking you might need to do.
#functools.wraps makes it so that the docstring and name of the returned wrapper function is the same.
If you need this_is_a_function to call the old whatever.this_is_a_function with arguments different than what was passed to it, you could do something like this:
import whatever
import functools
def wrap_function(oldfunction, newfunction):
#functools.wraps(function)
def run(*args, **kwargs):
return newfunction(oldfunction, *args, **kwargs)
return run
def this_is_a_function(oldfunc, parameter):
# Do some processing or something to customize the parameters to pass
newparams = parameter * 2 # Example of a change to newparams
return oldfunc(newparams)
whatever.this_is_a_function = wrap_function(
whatever.this_is_a_function, this_is_a_function)
There is a problem that if whatever is a pure C module, it's typically impossible (or very difficult) to change its internals in the first place.
So, here's an example of monkey-patching the time function from the time module.
import time
old_time = time.time
def time():
print('It is today... but more specifically the time is:')
return old_time()
time.time = time
print time.time()
# Output:
# It is today... but more specifically the time is:
# 1456954003.2
However, if you are trying to do this to C code, you will most likely get an error like cannot overwrite attribute. In that case, you probably want to subclass the C module.
You may want to take a look at this question.
This is the perfect time to tout my super-simplistic Hooker
def hook(hookfunc, oldfunc):
def foo(*args, **kwargs):
hookfunc(*args, **kwargs)
return oldfunc(*args, **kwargs)
return foo
Incredibly simple. It will return a function that first runs the desired hook function (with the same parameters, mind you) and will then run the original function that you are hooking and return that original value. This also works to overwrite a class method. Say we have static method in a class.
class Foo:
#staticmethod
def bar(data):
for datum in data:
print(datum, end="") # assuming python3 for this
print()
But we want to print the length of the data before we print out its elements
def myNewFunction(data):
print("The length is {}.".format(len(data)))
And now we simple hook the function
Foo.bar(["a", "b", "c"])
# => a b c
Foo.bar = hook(Foo.bar, myNewFunction)
Foo.bar(["x", "y", "z"])
# => The length is 3.
# => x y z
Actually, you can replace the target function's func_code. The example below
# a normal function
def old_func():
print "i am old"
# a class method
class A(object):
def old_method(self):
print "i am old_method"
# a closure function
def make_closure(freevar1, freevar2):
def wrapper():
print "i am old_clofunc, freevars:", freevar1, freevar2
return wrapper
old_clofunc = make_closure('fv1', 'fv2')
# ===============================================
# the new function
def new_func(*args):
print "i am new, args:", args
# the new closure function
def make_closure2(freevar1, freevar2):
def wrapper():
print "i am new_clofunc, freevars:", freevar1, freevar2
return wrapper
new_clofunc = make_closure2('fv1', 'fv2')
# ===============================================
# hook normal function
old_func.func_code = new_func.func_code
# hook class method
A.old_method.im_func.func_code = new_func.func_code
# hook closure function
# Note: the closure function's `co_freevars` count should be equal
old_clofunc.func_code = new_clofunc.func_code
# ===============================================
# call the old
old_func()
A().old_method()
old_clofunc()
output:
i am new, args: ()
i am new, args: (<__main__.A object at 0x0000000004A5AC50>,)
i am new_clofunc, freevars: fv1 fv2
I try to add unit test in python in function that save stats in a file
Here is the function for saving
def save_file_if_necessary(file_path, content, current_time, mode="w", delta_time=60, force=False):
if file_path not in file_save or current_time - file_save[file_path] >= delta_time or force:
with codecs.open(file_path, mode, encoding="utf-8") as written_file:
written_file.write(content)
file_save[file_path] = time.time()
print "yes"
return True
else:
print "not necessary"
return False
I make a call of this function like that
def test_function():
bot_url_dic = {"seven1": 10,
"seven2": 20
}
save_file_if_necessary(os.path.join("./", "recipients.bots"),json.dumps(bot_url_dic, ensure_ascii=False, indent=4), time.time())
And i made some unittest with mock to test if the function is called
from test import save_file_if_necessary, test_function
def test_call_save_file_if_necessary(self):
"""test function to test add in list."""
ip_dic = ["seven1", "seven2", "seven3"]
save_file_if_necessary = Mock()
test_function()
self.assertTrue(save_file_if_necessary.called)
But the problem is Mock is always return False but the function is called at least one time.
self.assertTrue(save_file_if_necessary.called)
AssertionError: False is not true
(python version 2.7.6)
All you've done is create a new Mock object, coincidentally called "save_file_if_necessary". You haven't done anything to replace the actual function with your mock.
You need to use the patch functionality to actually do that:
#mock.patch('my_test_module.save_file_if_necessary')
def test_call_save_file_if_necessary(self, mock_function):
ip_dic = ["seven1", "seven2", "seven3"]
test_function()
self.assertTrue(mock_file.called)
You need to import the module where the function is defined and assign a Mock to your function:
import test
def test_call_save_file_if_necessary(self):
"""test function to test add in list."""
ip_dic = ["seven1", "seven2", "seven3"]
test.save_file_if_necessary = Mock()
test.test_function()
self.assertTrue(test.save_file_if_necessary.called)
Or, use the patching function instead.