Why don't pytest fixtures work as intended?

3
votes

I'm trying to use PyTest and I cannot obtain how to set fixtures. I've tried the following code:

import pytest
import random

@pytest.fixture()
def setup():
    a = random.randint(0, 10)

def test(setup):
    assert 3 > a
if __name__ == '__main__':
    pytest.main()

And I am getting "NameError: name 'a' is not defined".

Also the example from the official documentation doesn't work. What's wrong? I need functionality similar to setUp/tearDown. But I don't want to use unittest. Can someone provide me an example with working fixtures (both setUp type and tearDown type)?

I want to write some test as functions and some test as methods inside classes. Therefore me second question is for an working example of using fixture with classes/methods. I just need to see working examples of fixtures in Python.

Is there a different Python 3 unit testing framework with assertions as simple as in PyTest?

2
pythonunit-testingpython-3.xfixturespytest

2 Answers

7
votes

Fixtures don’t work like this. They cannot magically transfer the name a from one function’s (setup) local scope to another’s (test). Instead, your setup function must explicitly return the object that will be passed as the setup argument to your test function. For example:

import pytest
import random

class TestSetup:
    def __init__(self):
        self.a = random.randint(0, 10)

@pytest.fixture()
def setup():
    return TestSetup()

def test(setup):
    assert 0 <= setup.a <= 10

if __name__ == '__main__':
    pytest.main()
1
votes

More typically you'd do something like:

/usr/bin/env python
import pytest
import random

@pytest.fixture()
def my_rand_int():
    return random.randint(0,10)

def test(my_rand_int):
    assert 3 > my_rand_int

if __name__ == '__main__':
    pytest.main()