[pytest-dev] Parametrized scope question

[holger krekel]

Hi Alex,

On Tue, Dec 15, 2015 at 09:18 +0000, Alex Netes wrote:
> Hi holger,
> 
> Thanks for your help.
> 
> > Hi Alex,
> > 
> > On Mon, Dec 14, 2015 at 15:50 +0000, Alex Netes wrote:
> >> Hello guys,
> >>
> >> I'm new to Pytest and I encounter something I cannot explain.
> > 
> > I also hit many things which i can not explain, even with pytest and maybe even with this very mail.
> > 
> 
> I'll try to explain my intention in behind my code, instead of showing my nitty code.
> 
> >> I'm trying to give fixture fixt_func() a parameter fixt_prm and expect the fixture to be called only
> >> once as it defined with 'class' scope, but the fixture is called twice as it ignores the scope. What am I
> >> missing?
> >>
> >>
> >> @pytest.fixture(scope='class')
> >> def fixt_func(request, resource, fixt_prm):
> >>     print fixt_prm
> >>
> >> class TestA():
> >>     @pytest.mark.parametrize('resource', ['x'], scope='class')
> >>     @pytest.mark.parametrize(fixt_prm ', ['x'], scope='class')
> >>     @pytest.mark.parametrize('prm', ['a', 'b'])
> >>     def test_a(self, prm, fixt_func)
> >>         assert True
> > 
> > You are doing something i wasn't aware is possible. You pass a parameter to the fixture function
> > fixt_func through parametrization but as a fixture.
> > In any case, if we modify your example to:
> > 
> >     import pytest
> >     @pytest.fixture(scope='class')
> >     def fixt_func(request, fixt_prm):
> >         print "fixt_func"
> > 
> >     class TestA():
> >         @pytest.mark.parametrize('fixt_prm', ['x', 'y'], scope='class')
> >         def test_a(self, fixt_func):
> >             assert True
> > 
> > this will also call fixt_func twice for the two executing tests.
> > It's argubaly "correct" behaviour from a certain point of view.
> > fixt_prm is class-scoped so each parameter instance exists as a different "class-level" value so we
> > interpret it to mean each class-scoped fixture function needs to be executed with both values.
> > 
> > Just imagine we wouldn't parametrize on the function directly but through a fixture function:
> > 
> >     import pytest
> >     @pytest.fixture(scope='class')
> >     def fixt_func(request, fixt_prm):
> >         print "fixt_func"
> > 
> >     @pytest.fixture(scope='class', params=["x", "y"])
> >     def fixt_prm(request):
> >         print "fixt_prm"
> > 
> >     class TestA():
> >         def test_a(self, fixt_func):
> >             assert True
> > 
> > Here it's maybe more obvious why this executes both fixture functions twice.
> > 
> > however, i am not sure about your precise example above.  I can see why you expect the two
> > different "prm" values (and thus test functions) to execute with the same class-level fixtures.  Maybe
> > others can chime in and say if they consider your example a bug or a "usual" behaviour.
> > 
> 
> Your examples makes sense. I'm trying to do something more complex and maybe I look at it in a wrong
> way. I want to define a fixture "fixt_func" so it would be able to receive a parameter defined by different
> test classes. Moreover I want "fixt_func" to have Class scope, so I can call finalize when all tests of the
> same class finished running. That's why I came up with the above "solution". 

I think you could use a marker on the class or even just a class attribute:

    import pytest
    
    @pytest.fixture(scope="class")
    def fix(request):
        return request.cls.attr * 10

    class TestA:
        attr = 1

        def test_one(self, fix):
            assert 0

    class TestB:
        attr = 2

        def test_one(self, fix):
            assert 0

The "request" object gives you back references into the context
of the test which requests fixtures.

HTH,
holger