pytest-lazy-fixture doesn't work for deep nesting

pytest-lazy-fixture doesn’t work for deep nesting

platform linux – Python 3.5.2, pytest-3.10.1, py-1.7.0, pluggy-0.8.1 plugins: timeout-1.3.0, celery-4.2.1, repeat-0.7.0, reportportal-1.0.4, assume-1.2, lazy-fixture-0.5.1

Example:

import pytest

@pytest.fixture(scope='function')
def fixt1():
    return 111

@pytest.fixture(scope='function')
def fixt2():
    return pytest.lazy_fixture("fixt1")

@pytest.fixture(scope='function')
def fixt3():
    return pytest.lazy_fixture("fixt2")

def test(fixt3):
    print("Value in test: {}".format(fixt3))

Returns:

Value in test: <LazyFixture "fixt1">

Should be:

Value in test: 111

[smarie]

This is a relatively old post, but pytest-cases might be a solution for you. Its parametrize_plus decorator supports referencing fixtures that are themselves parametrized, with fixture_ref.

In short pytest-cases provides a generalization of the great pytest-lazy-fixture to support more complex use-cases such as parametrization of lazy fixtures (and many other things such as fixture unions, etc.)

[YannickJadoul]

@bigbZik The main problem to get such a thing working on the long term is that pytest has two logical phases: first, all tests (with different parametrizations) are collected; and only then all tests (and necessary fixtures) are executed.

So in your example, only when fixt3 gets executed, pytest.lazy_fixture("fixt2") gets returned. So if fixt2 would be parametrized, there’d be no way for test to be instantiated multiple times during test collection.

But in this case, what’s the problem with these two alternatives?

import pytest

@pytest.fixture(scope='function')
def fixt1():
    return 111

@pytest.fixture(scope='function')
def fixt2(fixt1):
    return fixt1

@pytest.fixture(scope='function')
def fixt3(fixt2):
    return fixt2

def test(fixt3):
    print("Value in test: {}".format(fixt3))

or

import pytest

@pytest.fixture(scope='function')
def fixt1():
    return 111

@pytest.fixture(scope='function', params=[pytest.lazy_fixture('fixt1')])
def fixt2(request):
    return request.param

@pytest.fixture(scope='function', params=[pytest.lazy_fixture('fixt2')])
def fixt3(request):
    return request.param

def test(fixt3):
    print("Value in test: {}".format(fixt3))