Fixture execution order

[kracekumar]

import pytest


class Meh(object):
    @pytest.fixture(autouse=True)
    def a(self, request):
        print("meh")


class Foo(object):
    @pytest.fixture(autouse=True)
    def b(self):
        print("foo")


class Bar(object):
    @pytest.fixture(autouse=True)
    def c(self):
        print("bar")


class TestBaz(Meh, Bar, Foo):
    @pytest.fixture(autouse=True)
    def d(self):
        print("baz")

    def test_1(self):
        assert 1 == 1


class Meh1(object):
    @pytest.fixture(autouse=True)
    def foo(self, request):
        print("meh")


class Foo1(object):
    @pytest.fixture(autouse=True)
    def one(self):
        print("foo")


class Bar1(object):
    @pytest.fixture(autouse=True)
    def two(self):
        print("bar")


class TestBaz1(Meh1, Bar1, Foo1):
    @pytest.fixture(autouse=True)
    def three(self):
        print("baz")

    def test_1(self):
        assert 1 == 1

Output

(score)➜  score git:(master) ✗ py.test -s -v tests/integration_tests/test_test.py --pdb
============================================================================================================================= test session starts ==============================================================================================================================
platform darwin -- Python 2.7.6 -- py-1.4.27 -- pytest-2.7.0 -- /Users/krace/.virtualenvs/score/bin/python
rootdir: /Users/krace/code/score, inifile:
collected 2 items

tests/integration_tests/test_test.py::TestBaz::test_1 meh
foo
bar
baz
PASSED
tests/integration_tests/test_test.py::TestBaz1::test_1 meh
foo
baz
bar
PASSED

=========================================================================================================================== 2 passed in 0.03 seconds ===========================================================================================================================

I am using multiple classes with mixin approach to write test cases. Fixtures are executed alphabetically, not in the order.

I am expecting the fixtures to be run in Meh1 -> Foo1 -> Bar1 -> TestBaz1. Adding scope=class doesn't help. What am I doing wrong ?

[nicoddemus]

pytest currently doesn't try to take in account subclasses when executing fixtures.

One way to "enforce" one fixture to execute before the other is to make each fixture depend on a fixture of its subclass, for example make b fixture receive a a argument, or use pytest.mark.usefixtures.

One of the design goals for fixtures is modularity, so that fixtures can be used in different contexts without test functions knowing about them. An advantage of this is that fixtures can easily be defined at a module first and then later, when proven useful to be used in other tests/modules, moved to a conftest easily without changing tests themselves.

Hope that helps! 😄

[kracekumar]

Thanks. If it makes sense can we explicit add subclassing fixtures won't work in FAQ ?

[nicoddemus]

Sure, good idea. Could you open a PR? 😄

[kracekumar]

Yes, I will do it.