Let\'s say I have a class like this.
class SomeProductionProcess(CustomCachedSingleTon):
def loaddata():
\"\"\"
Uses an iterator
Here is a simple way to do it using mock
import mock
def new_loaddata(cls, *args, **kwargs):
# Your custom testing override
return 1
def test_SomeProductionProcess():
with mock.patch.object(SomeProductionProcess, 'loaddata', new=new_loaddata):
obj = SomeProductionProcess()
obj.loaddata() # This will call your mock method
I'd recommend using pytest
instead of the unittest
module if you're able. It makes your test code a lot cleaner and reduces a lot of the boilerplate you get with unittest.TestCase
-style tests.
Lets say you have a module named awesome.py and in it, you had:
import time
class SomeProductionProcess(CustomCachedSingleTon):
def loaddata(self):
time.sleep(30) # simulating a long running process
return 2
Then your unittest where you mock loaddata
could look like this:
import unittest
import awesome # your application module
class TestSomeProductionProcess(unittest.TestCase):
"""Example of direct monkey patching"""
def test_loaddata(self):
some_prod_proc = awesome.SomeProductionProcess()
some_prod_proc.loaddata = lambda x: 2 # will return 2 every time called
output = some_prod_proc.loaddata()
expected = 2
self.assertEqual(output, expected)
Or it could look like this:
import unittest
from mock import patch
import awesome # your application module
class TestSomeProductionProcess(unittest.TestCase):
"""Example of using the mock.patch function"""
@patch.object(awesome.SomeProductionProcess, 'loaddata')
def test_loaddata(self, fake_loaddata):
fake_loaddata.return_value = 2
some_prod_proc = awesome.SomeProductionProcess()
output = some_prod_proc.loaddata()
expected = 2
self.assertEqual(output, expected)
Now when you run your test, loaddata
wont take 30 seconds for those test cases.
To easily mock out a class method with a structured return_value, can use unittest.mock.Mock
.
from unittest.mock import Mock
mockObject = SomeProductionProcess
mockObject.loaddata = Mock(return_value=True)
EDIT:
Since you want to mock out the method with a custom implementation, you could just create a custom mock method object and swap out the original method at testing runtime.
def custom_method(*args, **kwargs):
# do custom implementation
SomeProductionProcess.loaddata = custom_method