I have a test suite (using nose, not unittest), and I want to patch a function to return a specific sequence of values for every test in the test class. My first attempt, using a simplified example, was:
#patch('time.clock', MagicMock(side_effects=[1, 2]))
class Tests:
def test_1(self):
assert time.clock() == 1
assert time.clock() == 2
def test_2(self):
assert time.clock() == 1
assert time.clock() == 2
However, the MagicMock instance is only created once, so the second test fails when the side effects run out. I can patch each test method separately, but I don't really want to duplicate the patch decorator over all of them (there are a lot more tests than in this example!) The other way I could do it is to create the patch in the setup code like this:
class Tests:
def setup(self):
self.old_clock = time.clock
time.clock = MagicMock(side_effects=[1, 2])
def teardown(self):
time.clock = self.old_clock
def test_1(self):
assert time.clock() == 1
assert time.clock() == 2
def test_2(self):
assert time.clock() == 1
assert time.clock() == 2
But saving and restoring the original function definition seems like something that Mock should be able to do automatically. Is there another method of doing this that I'm missing? Or is my last example the best way of doing this?
a = (x for x in [1,2])
x = lambda : next(a)
x()
Out: 1
x()
Out: 2
Put your answers into a's list.
Change X for your desired name.
You should just apply the patch to every test, instead of applying it to the class:
class Tests:
#patch('time.clock', MagicMock(side_effects=[1, 2]))
def test_1(self):
assert time.clock() == 1
assert time.clock() == 2
#patch('time.clock', MagicMock(side_effects=[1, 2]))
def test_2(self):
assert time.clock() == 1
assert time.clock() == 2
Related
I want to test a file called ninja.py wrote in Python3.6.
# File ninja.py
def what_to_do_result(result):
# Send a mail, write something in a file, play a song or whatever
def my_function(a, b):
# Step 1
result = a + b
# Step 2
if result == 3:
what_to_do_result(result)
elif result == 5:
what_to_do_result(result + 1)
else:
return True
I have started writing a test file called test_ninjapy and wrote some unittest. I do use Pytest.
import pytest
class MyTestException(Exception):
pass
def run_side_effect(*args, **kwargs):
raise MyTestException(kwargs["result"])
#pytest.fixture(name="resource")
def setup_fixture():
# Some code here
class TestNinja:
#staticmethod
def setup_method():
# Function called before each test
#staticmethod
def teardown_method():
# Function called after each test
#staticmethod
def test_my_function(mocker, resource):
# How to do this ???
mocker.patch("ninja.what_to_do_result", return_value=None, side_effect=run_side_effect)
# Then the test
assert 1 == 1 # -> This works
with pytest.raises(MyTestException):
ninja_function(a=1, b=2)
assert ninja_function(a=5, b=10)
The point is that I want to mock the function ninja.what_to_do_result and apply a side effect (= run a function).
I want the side effect to use the parameter (kwargs) or the function what_to_do_result.
But I don't know how to do this.
For example:
Because there are multiple possibilities (in the step 2, the call of what_to_do_result could be with 3 & 5, which are linked with 2 differents use cases I wxant to test.
Can you help me?
I did not found the related section in the documentation below.
Link to the documentation: https://github.com/pytest-dev/pytest-mock
I currently have the following basic Python class that I want to test:
class Example:
def run_steps(self):
self.steps = 0
while self.steps < 4:
self.step()
def step(self):
# some expensive API call
print("wasting time...")
time.sleep(1000)
self.steps += 1
As you can see, the step() method contains an expensive API call so I want to mock it with another function that avoids the expensive API call but still increments self.steps. I found that this is possible by doing this (as seen from here):
def mock_step(self):
print("skip the wasting time")
self.steps += 1
# This code works!
def test(mocker):
example = Example()
mocker.patch.object(Example, 'step', mock_step)
example.run_steps()
I simply create a function called mock_step(self) that avoids the API call, and I patch the original slow step() method with the new mock_step(self) function.
However, this causes a new problem. Since the mock_step(self) function is not a Mock object, I can't call any of the Mock methods on it (such as assert_called() and call_count()):
def test(mocker):
example = Example()
mocker.patch.object(Example, 'step', mock_step)
example.run_steps()
# this line doesn't work
assert mock_step.call_count == 4
To solve this issue, I have tried to wrap mock_step with a Mock object using the wraps parameter:
def test(mocker):
example = Example()
# this doesn't work
step = mocker.Mock(wraps=mock_step)
mocker.patch.object(Example, 'step', step)
example.run_steps()
assert step.call_count == 4
but then I get a different error saying mock_step() missing 1 required positional argument: 'self'.
So from this stage I am not sure how I can assert that step() has been called exactly 4 times in run_steps().
There are several solutions to this, the simplest is probably using a standard mock with a side effect:
def mock_step(self):
print("skip the wasting time")
self.steps += 1
def test_step(mocker):
example = Example()
mocked = mocker.patch.object(Example, 'step')
mocked.side_effect = lambda: mock_step(example)
example.run_steps()
assert mocked.call_count == 4
side_effect can take a callable, so you can both use a standard mock and the patched method.
import unittest.mock as mock
from functools import partial
def fake_step(self):
print("faked")
self.steps += 1
def test_api():
api = Example()
with mock.patch.object(api, attribute="step", new=partial(fake_step, self=api)):
# we need to use `partial` to emulate that a real method has its `self` parameter bound at instantiation
api.run_steps()
assert api.steps == 4
Correctly outputs "faked" 4 times.
This is a continuation of the SO question asked here but with a more complicated pattern than originally requested. My main intention is to try to mock an API call based on values passed to its caller. The API call has no idea of the values passed to its caller but needs to provide the correct behavior so that the caller can be tested fully. I am using time to determine which behavior I want when I want it.
Given a an object:
# some_object.py
from some_import import someApiCall
class SomeObject():
def someFunction(time, a, b, c):
apiReturnA = someApiCall(a)
returnB = b + 1
apiReturnC = someApiCall(c)
return [apiReturnA, returnB, apiReturnC]
that is created by another object with entry point code:
# some_main.py
import some_object
class myMainObject():
def entry_point(self, time):
someObj = some_object.SomeObject()
if 'yesterday' == time:
(a, b, c) = (1, 1, 1)
elif 'today' == time:
(a, b, c) = (2, 2, 2)
elif 'later' == time:
(a, b, c) = (3, 3, 3)
elif 'tomorrow' == time:
(a, b, c) = (4, 4, 4)
else:
return "ERROR"
return someObj.someFunction(time, a, b, c)
how can I get someApiCall to change based on the time argument?
# some_import.py
def someApiCall(var):
print("I'm not mocked! I'm slow, random and hard to test")
return var + 2
Here is an example test case
# test_example.py
import some_main
def amend_someApiCall_yesterday(var):
# Reimplement api.someApiCall
return var * 2
def amend_someApiCall_today(var):
# Reimplement api.someApiCall
return var * 3
def amend_someApiCall_later(var):
# Just wrap around api.someApiCall. Call the original function afterwards. Here we can also put
# some conditionals e.g. only call the original someApiCall if the var is an even number.
import some_import
var *= 4
return some_import.someApiCall(var)
def someObject_decorator_patch(someFunction, mocker, *args):
def wrapper(time, a, b, c):
# If x imports y.z and we want to patch the calls to z, then we have to patch x.z. Patching
# y.z would still retain the original value of x.z thus still calling the original
# functionality. Thus here, we would be patching src.someApiCall and not api.someApiCall.
if time == "yesterday":
mocker.patch("some_object.someApiCall", side_effect=amend_someApiCall_yesterday)
elif time == "today":
mocker.patch("some_object.someApiCall", side_effect=amend_someApiCall_today)
elif time == "later":
mocker.patch("some_object.someApiCall", side_effect=amend_someApiCall_later)
elif time == "tomorrow":
mocker.patch("src.someApiCall", return_value=0)
else:
# Use the original api.someApiCall
pass
return someFunction(time, a, b, c)
return wrapper
def test_some_main(mocker):
results = 0
uut = some_main.myMainObject()
times = ['yesterday', 'today', 'later', 'tomorrow']
mocker.patch.object(some_main.some_object.SomeObject, 'someFunction', someObject_decorator_patch)
for time in times:
results = uut.entry_point(time)
print(results)
assert 0 != results
The test case doesn't get the result I want (it returns a function pointer).
Here is an improvised solution of https://stackoverflow.com/a/67498948/11043825 without using decorators.
As already pointed out, we still need to intercept the calls to the function that accepts the time argument which indicates how someApiCall would behave, which is either entry_point or someFunction. Here we would intercept someFunction.
Instead of implementing python decorator on someFunction which then needs to call that explicitly created decorated function, here we would amend (well this still follows the decorator design pattern) the someFunction in-place and make it available to the rest of the source code calls without explicitly changing the call to the decorated function. This is like an in-place replacement of the original functionalities, where we would replace (or rather wrap around) the original functionality with an updated one which would perform an assessment of the time before calling the original functionality.
Also for your reference, I solved it for 2 types of functions, a class method src.SomeClass.someFunction and a global function src.someFunction2.
./_main.py
import src
class MyMainClass:
def __init__(self):
self.var = 0
def entry_point(self, time):
someObj = src.SomeClass()
self.var += 1
if self.var >= 10:
self.var = 0
ret = f'\n[1]entry_point({time})-->{someObj.someFunction(time, self.var)}'
self.var += 1
ret += f'\n[2]entry_point({time})-->{src.someFunction2(time, self.var)}'
return ret
./src.py
class SomeClass:
def someFunction(self, time, var):
return f'someFunction({time},{var})-->{someSloowApiCall(var)}'
def someFunction2(time, var):
return f'someFunction2({time},{var})-->{someSloowApiCall2(var)}'
./api.py
def someSloowApiCall(var):
return f'someSloowApiCall({var})-->{special_message(var)}'
def someSloowApiCall2(var):
return f'someSloowApiCall2({var})-->{special_message(var)}'
def special_message(var):
special_message = "I'm not mocked! I'm slow, random and hard to test"
if var > 10:
special_message = "I'm mocked! I'm not slow, random or hard to test"
return special_message
./test_main.py
import _main, pytest, api
def amend_someApiCall_yesterday(var):
# Reimplement api.someSloowApiCall
return f'amend_someApiCall_yesterday({var})'
def amend_someApiCall_today(var):
# Reimplement api.someSloowApiCall
return f'amend_someApiCall_today({var})'
def amend_someApiCall_later(var):
# Just wrap around api.someSloowApiCall. Call the original function afterwards. Here we can also put
# some conditionals e.g. only call the original someSloowApiCall if the var is an even number.
return f'amend_someApiCall_later({var})-->{api.someSloowApiCall(var+10)}'
def amend_someApiCall_later2(var):
# Just wrap around api.someSloowApiCall2. Call the original function afterwards. Here we can also put
# some conditionals e.g. only call the original someSloowApiCall2 if the var is an even number.
return f'amend_someApiCall_later2({var})-->{api.someSloowApiCall2(var+10)}'
def get_amended_someFunction(mocker, original_func):
def amend_someFunction(self, time, var):
if time == "yesterday":
mocker.patch("_main.src.someSloowApiCall", amend_someApiCall_yesterday)
# or
# src.someSloowApiCall = amend_someApiCall_yesterday
elif time == "today":
mocker.patch("_main.src.someSloowApiCall", amend_someApiCall_today)
# or
# src.someSloowApiCall = amend_someApiCall_today
elif time == "later":
mocker.patch("_main.src.someSloowApiCall", amend_someApiCall_later)
# or
# src.someSloowApiCall = amend_someApiCall_later
elif time == "tomorrow":
mocker.patch("_main.src.someSloowApiCall", lambda var: f'lambda({var})')
# or
# src.someSloowApiCall = lambda var: 0
else:
pass
# or
# src.someSloowApiCall = someSloowApiCall
return original_func(self, time, var)
return amend_someFunction
def get_amended_someFunction2(mocker, original_func):
def amend_someFunction2(time, var):
if time == "yesterday":
mocker.patch("_main.src.someSloowApiCall2", amend_someApiCall_yesterday)
# or
# src.someSloowApiCall2 = amend_someApiCall_yesterday
elif time == "today":
mocker.patch("_main.src.someSloowApiCall2", amend_someApiCall_today)
# or
# src.someSloowApiCall2 = amend_someApiCall_today
elif time == "later":
mocker.patch("_main.src.someSloowApiCall2", amend_someApiCall_later2)
# or
# src.someSloowApiCall2 = amend_someApiCall_later
elif time == "tomorrow":
mocker.patch("_main.src.someSloowApiCall2", lambda var : f'lambda2({var})')
# or
# src.someSloowApiCall2 = lambda var: 0
else:
pass
# or
# src.someSloowApiCall2 = someSloowApiCall2
return original_func(time, var)
return amend_someFunction2
#pytest.mark.parametrize(
'time',
[
'yesterday',
'today',
'later',
'tomorrow',
'whenever',
],
)
def test_entrypointFunction(time, mocker):
mocker.patch.object(
_main.src.SomeClass,
"someFunction",
side_effect=get_amended_someFunction(mocker, _main.src.SomeClass.someFunction),
autospec=True, # Needed for the self argument
)
# or
# src.SomeClass.someFunction = get_amended_someFunction(mocker, src.SomeClass.someFunction)
mocker.patch(
"_main.src.someFunction2",
side_effect=get_amended_someFunction2(mocker, _main.src.someFunction2),
)
# or
# src.someFunction2 = get_amended_someFunction2(mocker, src.someFunction2)
uut = _main.MyMainClass()
print(f'\nuut.entry_point({time})-->{uut.entry_point(time)}')
Output:
$ pytest -rP
=================================== PASSES ====================================
_____________________ test_entrypointFunction[yesterday] ______________________
---------------------------- Captured stdout call -----------------------------
uut.entry_point(yesterday)-->
[1]entry_point(yesterday)-->someFunction(yesterday,1)-->amend_someApiCall_yesterday(1)
[2]entry_point(yesterday)-->someFunction2(yesterday,2)-->amend_someApiCall_yesterday(2)
_______________________ test_entrypointFunction[today] ________________________
---------------------------- Captured stdout call -----------------------------
uut.entry_point(today)-->
[1]entry_point(today)-->someFunction(today,1)-->amend_someApiCall_today(1)
[2]entry_point(today)-->someFunction2(today,2)-->amend_someApiCall_today(2)
_______________________ test_entrypointFunction[later] ________________________
---------------------------- Captured stdout call -----------------------------
uut.entry_point(later)-->
[1]entry_point(later)-->someFunction(later,1)-->amend_someApiCall_later(1)-->someSloowApiCall(11)-->I'm mocked! I'm not slow, random or hard to test
[2]entry_point(later)-->someFunction2(later,2)-->amend_someApiCall_later2(2)-->someSloowApiCall2(12)-->I'm mocked! I'm not slow, random or hard to test
______________________ test_entrypointFunction[tomorrow] ______________________
---------------------------- Captured stdout call -----------------------------
uut.entry_point(tomorrow)-->
[1]entry_point(tomorrow)-->someFunction(tomorrow,1)-->lambda(1)
[2]entry_point(tomorrow)-->someFunction2(tomorrow,2)-->lambda2(2)
______________________ test_entrypointFunction[whenever] ______________________
---------------------------- Captured stdout call -----------------------------
uut.entry_point(whenever)-->
[1]entry_point(whenever)-->someFunction(whenever,1)-->someSloowApiCall(1)-->I'm not mocked! I'm slow, random and hard to test
[2]entry_point(whenever)-->someFunction2(whenever,2)-->someSloowApiCall2(2)-->I'm not mocked! I'm slow, random and hard to test
============================== 5 passed in 0.07s ==============================
I'm having some issue while creating unittest for internal parameter.
My structure is:
[1] my_animal.py contains Myclass and method: do_bite()
my_animal.py
class Myclass():
def do_bite(self):
return 1
[2] my_module.py contains jobMain("") which is using the method from my_animal.py
my_module.py
import sys
from someclass import Myclass
def jobMain(directoryPath):
flag = -1
result = Myclass()
if result.do_bite() is None:
flag = 0
if result.do_bite() is 1:
flag = 1
if result.do_bite() is 2:
flag = 2
[3] my_test.py contains the unittest to test jobMain in my_module.py
my_test.py
# Mock Myclass.dobite to None
#pytest.fixture
def mock_dobite0():
with mock.patch('my_module.Myclass') as mocked_animal:
mocked_animal.return_value.do_bite.return_value = None
yield
# Mock Myclass.dobite to 1
#pytest.fixture
def mock_dobite1():
with mock.patch('my_module.Myclass') as mocked_animal:
mocked_animal.return_value.do_bite.return_value = 1
yield
# Mock Myclass.dobite to 2
#pytest.fixture
def mock_dobite2():
with mock.patch('my_module.Myclass') as mocked_animal:
mocked_animal.return_value.do_bite.return_value = 2
yield
# My unittest to test dobite() method
def test_dobite0(mock_Myclass, mock_dobite0):
jobMain("")
def test_dobite1(mock_Myclass, mock_dobite1):
jobMain("")
def test_dobite2(mock_Myclass, mock_dobite2):
jobMain("")
My question is: How to test 'flag' parameter inside JobMain?
'flag' para must be assigned the correct value.( eg: dobite = 1 => flag = 1)
The variable para only exists in the scope of jobMain. If you want to use the variable outside jobMain the most common ways are
1) return the value
This is quite obvious. Since jobMain is a function, it returns a value. Without an explicit return statement you return None. You could just
def jobmain(pth):
# do stuff and assign flag
return flag
# and inside tests
assert jobmain("") == 1
2) Use a class instead
If you want the jobMain to remember some state, then it is common practice to use objects. Then flag would be attribute of the object and could be accessed from outside, after you call any method (function) of JobMain. For example
class JobMain:
def __init__(self):
self.flag = -1
def run(self, pth):
result = Myclass()
if result.do_bite() is None:
self.flag = 0
if result.do_bite() is 1:
self.flag = 1
if result.do_bite() is 2:
self.flag = 2
# and inside test
job = JobMain()
job.run()
assert job.flag == 1
Note
I just copy-pasted your code for setting the flag. Note that you call do_bite() many times, if the resulting value is None or 1. Also, when testing against a number, one should use == instead of is.
How to test 'flag' parameter inside JobMain?
You don't. It's an internal variable. Testing it would be glass-box testing; the test will break if the implementation changes.
Instead, test the effect of flag. This is black-box testing. Only the interface is tested. If the implementation changes the test still works allowing the code to be aggressively refactored.
Note: If you don't hard code result = Myclass() you don't need to mock. Pass it in as an argument with the default being Myclass().
def jobMain(directoryPath, result=Myclass()):
Then you don't need to patch Myclass(). Instead, pass in a mock object.
# I don't know unittest.mock very well, but something like this.
mock = Mock(Myclass)
mock.do_bite.return_value = 2
jobMain('', result=mock)
This also makes the code more flexible outside of testing.
I have the following test that does not fail when running an especially long fib assert.
Tests that don't fail properly
#!/usr/env/bin python2.7
import unittest
from fib import fib
from nose.tools import timed
def test_gen(expected, actual):
#timed(.001)
def test_method(self):
return self.assertEqual(expected, actual)
return test_method
if __name__ == '__main__':
all_cases = {
'user': ((fib(40), 102334155), (fib(2), 1), (fib(5), 5)),
}
fails = {}
for username, cases in all_cases.items():
class FibTests(unittest.TestCase):
pass
for index, case in enumerate(cases):
test_name = 'test_{0}_{1}'.format(username, index)
test = test_gen(case[1], case[0])
setattr(FibTests, test_name, test)
suite = unittest.TestLoader().loadTestsFromTestCase(FibTests)
result = unittest.TextTestRunner(verbosity=2).run(suite)
fails[username] = len(result.failures)
print fails
(Slow) Fib.py Implementation
def fib(x):
if x == 0:
return 0
elif x == 1:
return 1
return fib(x - 2) + fib(x - 1)
Tests that fail properly
import unittest
from fib import fib
from nose.tools import timed
def test_gen(expected, actual):
#timed(.001)
def test_method(self):
time.sleep(.2)
return self.assertEqual(expected, actual)
return test_method
You are timing the wrong thing, and never actually calling your test method. You are also going to an awful lot of effort to dynamically create and add your cases to your class that does nothing but act as a container for tests when nose supports generator test cases, which would be much easier to read and follow than what you have here. Also, is this a test file or a piece of product code? If it's a test file, then having all of that code in if __name__ == '__main__' is kind of odd, and if it is a product code file, then having the test_gen function and the unittest and nose import statements in the uncoditionally run part doesn't make much sense. I'd recommend doing it the following way, and not trying to make the test script self-runnable; just launch it with nose.
from fib import fib
from nose.tools import timed
fib = timed(.001)(fib)
def execute(username, fib_arg, expected_output):
result = fib(fib_arg)
assert result == expected_output, ('%s fib(%d) got %d, expected %d'
% (username, fib_arg, result, expected_output))
def test_fib():
for name, datasets in (('user', ((40, 102334155), (2, 1), (5, 5))),):
for arg, expected in datasets:
yield execute, name, arg, expected