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

[Dr Keith M Franklin]

I do actually normally write the finalizers function outside of the fixture so it can be reused in tests, but from what I can see that doesn’t tie you into using “addfinalizer” as I’m guessing you could just make a call the function on return from the yield.

Thanks for all the feedback, I thought that it might be the case that both are basically the same.  However, I wanted to check and also see if there is a more “approved/appropriate” method or if it was just stylistic preference.

Keith


> On 4 Dec 2017, at 13:27, Floris Bruynooghe <flub at devork.be> wrote:
> 
> 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,
>>> 
>> 
>> 
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