Multiple copies of a pytest fixture

Question

Let’s say I have a simple fixture like the following (using pytest-django, but it applies to pytest as well):

@pytest.fixture
def my_thing(request, db):
    thing = MyModel.objects.create()
    request.addfinalizer(lambda: thing.delete())
    return thing

This works great when my tests need a single instance of MyModel. But what about if I need two (or three or four)? I want each instance to be distinct, but to be set up in the same way.

I could copy/paste the code and rename the fixture function, but that seems inelegant.

Similarly, I have tried:

@pytest.fixture
def my_thing_1(my_thing):
    return my_thing

@pytest.fixture
def my_thing_2(my_thing):
    return my_thing

However, each of these appears to return the same instance of MyModel.

Is there a way to do what I want using pytest’s built-in functionality? Alternately, I could move the setup/teardown of my fixture out into helper functions so I’m not duplicating too much code.

Or am I going about this whole thing the wrong way?

Asked By: Frank T

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Answer 1

My approach would probably to create a fixture which can generate your objects:

@pytest.fixture
def thing(request, db):
    class ThingFactory(object):
        def get(self):
            thing = MyModel.objects.create()
            request.addfinalizer(thing.delete)
            return thing
    return ThingFactory()

def test_thing(thing):
    thing1 = thing.get()
    thing2 = thing.get()

Obviously you can make .get() take an argument etc.

(PS: Also note there’s no need for the lambda in the finalizer)

Answered By: flub

Answer 2

I’m arriving at this question very late… but, using a parametrized fixture and simply returning the fixture you want to duplicate seems to work too.

import pytest
import random

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


@pytest.fixture(params=[0, 1])
def parametrized_name(request, name):
    return name


def test_something(parametrized_name):
    print "Testing with name: " + str(parametrized_name)

If you run the above test, you get 2 different “name” fixtures

$ pytest -s blah.py
============================================= test session starts ==============================================
platform linux2 -- Python 2.7.14, pytest-3.3.2, py-1.5.2, pluggy-0.6.0
rootdir: /home/bsquizza/repos/blah/tests, inifile:
collected 2 items                                                                                              

blah.py Testing with name: 7
.Testing with name: 10
.                                                                                               [100%]

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

Answered By: Brandon Squizzato

Multiple copies of a pytest fixture

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