is it possible to pass an object or variable from test function to a function fixture?

Question

In pytest I'm trying to figure out if its possible to pass an object or variable to a "function scope" fixture from a test function(either to the fixture setup or teardown)

It's impossible to pass anything from the test to fixture setup because the test will run after the setup has already finished. Passing anything to fixture's teardown is possible via e.g. global variables or an attribute of the object returned by the fixture etc. — hoefling

gbajson gbajson · Accepted Answer · 2019-08-16T09:38:57

You might interact with the fixture as follows, but it's not in the setup or teardown:

Code

import pytest

class FixtureStack():
    def __init__(self):
        self.messages = []

    def __str__(self):
        return f'messages={self.messages}'

    def push(self, msg):
        self.messages.append(msg)


@pytest.fixture(scope='function')
def stack():
    yield FixtureStack()


def test_1(stack):
    print(stack)
    stack.push('msg_1')
    print(stack)
    assert stack.messages == ['msg_1']


def test_2(stack):
    print(stack)
    stack.push('msg_2')
    print(stack)
    assert stack.messages == ['msg_2']

Pytest execution:

$ pytest -v driver.py -s
=============================================== test session starts ================================================
platform linux -- Python 3.7.1, pytest-5.0.1, py-1.7.0, pluggy-0.12.0 -- /home/backend/venvs/py3.7.1/bin/python3.7
cachedir: .pytest_cache
rootdir: /home/backend/backend, inifile: pytest.ini
plugins: mock-1.10.4
collected 2 items

driver.py::test_1 messages=[]
messages=['msg_1']
PASSED
driver.py::test_2 messages=[]
messages=['msg_2']
PASSED

============================================= 2 passed in 0.01 seconds =============================================

is it possible to pass an object or variable from test function to a function fixture?

1 Answers