[py-dev] Does each test method get called with a new instance?

[holger krekel]

Hi Roy, 

On Tue, Apr 05, 2005 at 17:11 -0400, Roy Smith wrote:
> Most of the time, all I'm really interested in is that I've got a fresh 
> instance of the class being tested.  While it may be true that old 
> instances (from previous test methods) may not have been finalized yet, 
> that's only going to be of concern when there's something significant to 
> finalize (i.e. close a file handle or something like that).  In those 
> specific (but rare) cases, I could then use the teardown() hook to clean 
> things up, and most of the time I could get away without a teardown().

I think i understand your resoning. 

> This way, it seems like I need to do:
> 
> def setup_method (self, method):
>    self.testInstance = ClassUnderTest()
> 
> def teardown_method (self, method):
>    del self.testInstance
> 
> to get a clean instance for every test method. 
>
> This I get for free with unittest.  And of course with this,
> everyplace I'd normally use self.foo in my test methods, I'd
> now have to use self.testInstance.foo.

Not quite, instead of writing 

    def __init__(self): 
        ... 

you just write 

    def setup_method(self, method): 
        ... 

and be done with it.  This makes it very explicit in which 
scope your code will be invoked, doesn't it? 

It seems a common use case that people want to customize per test
method invocation (after all, that's what unittest's setUp() does) 
so there is a need for setup_method/teardown_method, anyway. 
But why offer a second way (per __init__ which doesn't know about
the method) to do the same thing in a more restricted way? 

> Or am I just not getting it?

test state management is actually a pretty involved issue. 
py.test tries to provide very explicit hooks where their names
leave as few doubts about when and in which way they will
be invoked.

cheers, 

    holger