[pytest-dev] Question about fixtures and the use of finalizers vs yield

[Floris Bruynooghe]

Another often-overlooked benefit of request.addfinalizer() is that it
can also be used in a test directly for one-off finalization:

def test_foo(request):
    # arrange: set some stuff up just for this test
    request.addfinalizer(lambda: ...) # clean global state of thing setup
    # act
    # assert

But as said, if you're in a fixture and only use one .addfinalizer()
call there is no difference at all between it and the yield version.
It's just a matter of style.


On 4 December 2017 at 13:43, Ernesto D. Luzon Jr. <edluzonjr at gmail.com> wrote:
>
> PyTest fixtures using addfinalizer() become convenient when you want to make
> them work in RobotFramework as well.
>
> def fixture_being_used_in_robotframework():
>     closure = "details of how to cleanup the fixture"
>
>
>     def clean_up():
>         print(closure)
>
>     return clean_up
>
>
> @pytest.fixture()
> def reuse_robotframework_fixture(request):
>     request.addfinalizer(fixture_being_used_in_robotframework())
>
>
> Cheers,
> Ernesto
>
>
>
>>
>>
>> Message: 3
>> Date: Mon, 4 Dec 2017 11:49:24 +0000
>> From: Dr Keith M Franklin <keith.franklin at gmail.com>
>> To: pytest-dev at python.org
>> Subject: [pytest-dev] Question about fixtures and the use of
>>         finalizers vs yield
>> Message-ID: <D7E4FF9A-6EE8-404B-8654-C1F7EE9E47A3 at gmail.com>
>> Content-Type: text/plain; charset=utf-8
>>
>>
>> Good morning/afternoon,
>>
>> I hope this is the right place to post this.  I?ve been using PyTest for a
>> while but recently come across someone else?s fixture which made me wonder
>> if I?m doing this right.  Basically I?ve been creating a fixture like and
>> adding a finalizer like so:
>>
>> @pytest.fixture(scope=?function?)
>> def my_fixture(request):
>>   # Code that does something e.g. creates a database record
>>   rec = DBObject()
>>
>>   def clean_up():
>>       # Code required to clean up the fixture code and return the state
>> back to the
>>       ...
>>   request.addfinalizer(clean_up)
>>   return rec
>>
>>
>> However, I?ve seen fixtures written using yield instead e.g.
>>
>>
>> @pytest.fixture(scope=?function?)
>> def my_fixture(request):
>>   # Code that does something e.g. creates a database record
>>   rec = DBObject()
>>   yield rec
>>
>>   # Code required to clean up the fixture code and return the state back
>> to the
>>   ...
>>
>> Can I ask, is there any real difference between the two approaches?  Is
>> there a preferred method and if so why?
>>
>> Thanks in advance for any help.
>>
>> Keith
>>
>> ------------------------------
>>
>> Message: 4
>> Date: Mon, 04 Dec 2017 12:14:42 +0000
>> From: Bruno Oliveira <nicoddemus at gmail.com>
>> To: Dr Keith M Franklin <keith.franklin at gmail.com>
>> Cc: pytest-dev at python.org
>> Subject: Re: [pytest-dev] Question about fixtures and the use of
>>         finalizers vs yield
>> Message-ID:
>>
>> <CA+RQFff9Cx-P_Vs4jcU=cCQHy=mwuuRauU0vQEv7wdF=cZKv+A at mail.gmail.com>
>> Content-Type: text/plain; charset="utf-8"
>>
>> Hi Keith,
>>
>> Both approaches are valid and identical; I personally prefer using yield
>> because to me it feels more natural.
>>
>> Cheers,
>>
>
>
> _______________________________________________
> pytest-dev mailing list
> pytest-dev at python.org
> https://mail.python.org/mailman/listinfo/pytest-dev
>