Python unit testing overriding module level functions
python, python-2.7
Solution
I don't know if it's the best way, but I generally use `try ... finally` when I'm doing this in tests, in order to set then restore changes during each test.
A brief example of this:
class TestRawInput(unittest.TestCase):
def test_raw_input(self):
orig_raw_input = raw_input
try:
raw_input = lambda _: 'Alice'
self.assertEquals(raw_input(), 'Alice')
finally:
raw_input = orig_raw_input
An alternative could be to create a context manager for doing this, if it's a common operation in tests.
Problem
Related to Python unit testing code which calls OS/Module level python functions. During my unit testing I overload some python system calls to get my tests to drive different paths of a module. This technique called Monkey Patch (in the related question) for tests in isolation. I am a bit worried about what happens when I run Python tests in parallel say like in "Nose". What happens when two tests are run in parallel and both want to mock the os.path.exists method? Is there a way to selectively override a system or module function in the context of my test? Take the following for example ``` fixture.py (say that is the module under test) def my_func(): some_stuff test_fixture.py (say this is my test case) class MyTest(unittest.TestCase): def test_mine(self): fixture.my_func = my_new_func fixture.execute_some_func_that_calls_my_func() #What happens if another test is executing at the same time and accesses #my_func I don't want it to start executing my_new_func? ```