[pytest-dev] Parametrized scope question

[Alex Netes]

Hi holger,

> 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.

Thanks. I think marker option better suite my needs. However, I have two questions.
1. I hit a problem with getting marker parameter from the fixture when it defined
with 'class' scope. When I remove the scope, it works.

     Import pytest

    @pytest.fixture(scope="class")
    def fix(request):
        print request.node.get_marker('attr') # None

    @pytest.mark.attr('something')
    class TestA:
        def test_one(self, fix):
            assert 0

     ------------------------------
     Import pytest

    @pytest.fixture
    def fix(request):
        print request.node.get_marker('attr') # <MarkInfo 'attr' args=('something',) kwargs={}>

    @pytest.mark.attr('something')
    class TestA:
        def test_one(self, fix):
            assert 0

2. Is it possible to provide arguments to the marker via the command line?