[py-dev] parametrized resources (Re: Generic funcarg hook)

[holger krekel]

Hi Floris, all, 

On Tue, Aug 10, 2010 at 11:01 +0200, holger krekel wrote:
> FYI, i am considering introducing a slightly higher level 
> mechanism on top of funcargs, dealing with (parametrizable)
> resources.  Something like:
> 
> @py.test.mark.resourcefactory(scope="session", argnames=['foo', 'bar'])
> def myfactory(request):
>     if request.argname == "foo":
>         ...
>     elif request.argname == "bar":
>         ... 
> 
> The request object would be what pytest_funcarg__NAME get but
> this would allow free naming and have a single factory become
> responsible for multiple funcargs and allow to declare scope
> reather than having to invoke request.cached_setup().  Instead
> of the latter, one could write "request.addfinalizer()" which
> would default to the declared scope. 

just to be clear, the test function would look like:

    def test_function(foo):
        ... foo is initialized per-session, created per the factory above

    def test_function2(foo, bar):
        ... foo and bare are created by two invocations to the factory above

Moreover, regarding the "parametrized resources" aspect, 
there would be a new decorator:  

    @py.test.mark.parametrize(foo=iterable)
    def test_function(foo):
        ... invoked for multiple foo instances

The idea is to be able to avoid pytest_generate_tests functions
in a number of cases.  

Both the current funcarg-mechanism and the generate-tests mechanism
would continue to exist but be considered "lower level", i.e. upcoming
examples on the web page would use the new more declarative approach,
requiring less API knowledge and naming freedom to use them. 

any comments and particularly real use cases very welcome! 

best,
holger
 
> Happy about any thoughts on this but mainly i mention this
> consideration here in case it would fit with your use case. 
> 
> best,
> holger
> 
> 
> On Sat, Aug 07, 2010 at 10:52 +0100, Floris Bruynooghe wrote:
> > Hi
> > 
> > I was talking to ronny on IRC about wanting a generic funcarg hook and
> > he asked me to post my use case here as you are still thinking about
> > the API for it.  Since there is no generic funcarg hook now this is
> > how I currently create the tests:
> > 
> > 
> > def pytest_funcarg__tdata(request):
> >     fname = os.path.join(DATADIR, requst.function.__name__+'.ext')
> >     with file(fname) as fd:
> >         obj = fd.read()
> >     return obj
> > 
> > def test_spam(tdata):
> >     assert func_under_test(tdata) == 'foo'
> > 
> > def test_eggs(tdata):
> >     assert func_under_test(tdata) == 'bar'
> > 
> > 
> > Before I started writing it this way I was looking for a generic
> > funcarg hook since I think this would have been clearer if I could
> > have used "spam" and "eggs" as funcargs and still create the object
> > for them from one function rather then having to spell it out for each
> > one.  So I'm hoping that in a future version you might add an API to
> > do allow something like this.
> > 
> > -- 
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