Re: [Pyunit-interest] Feature Request: Cleanup Registry

[Ype K. <yk...@xs...>]

Jim,

I made a similar proposal some time ago. Below is the reply
of Steve Purcell. He convinced me.

Jim wrote:
>Problem
>
>  the Zope 3 project is making extensive use of PyUnit.  Zope 3 unit
>  tests often have to register components with various component
>  registries. These registrations need to be torn down after each
>  test. This became very tedious. For this reason, we've implemented a
>  cleanup registry. Any stateful global objects, like component
>  registries register functions with this cleanup registry. Test
>  classes provide tearDown methods that call a method on the cleanup
>  registry, which calls all the registered functions.  This is an
>  extremely useful pattern that might be beneficial to other
>  projects. Further, it would be nice if test classes didn't have to
>  provide a tear-down method that just called the cleanup registry (or
>  mix-in a class that provided such a tearDown.
>
>Proposal
>
>  Add a cleanup registry to the unittest module.  The unittest module
>  would provide an additional function, addCleanUp, which takes a
>  callable object to be called without arguments after running each
>  unit test. After each test, and after running the test class's
>  tearDown method, each registered cleanup callable will be called.
>
>  Suppose there was an application module with a global dictionary
>  that was manipulated by application routines:
>
>     TheData = {}
>
>  The module would register the clear method of this dictionary with
>  unittest.addCleanUp to make sure the dictionary was reinitialized
>  after each test:
>
>     import unittest
>     unittest.addCleanUp(TheData.clear)
>
>I'd be happy to provide a patch.


This is Steve's reply to my post:

Date: Sun, 23 Sep 2001 13:38:09 +0200
From: Steve Purcell <ste...@ya...>
To: Ype Kingma <yk...@xs...>
Cc: pyu...@li...

Subject: Re: [Pyunit-interest] setup/teardown for a TestSuite


Hi Ype,

Previous discussion on this list of this topic may be hidden behind obscure
subject lines; you're not the first to suggest a setUp and tearDown for
TestSuite.

However, this defeats one of the central ideas of the framework, which is
that each test should be able to run either in isolation or in arbitrary
combination with other tests. That is, each test case should provide for the
setting up and tidying up of the environment in which it runs.

Test cases need not even run as part of a suite:

   class MyTestCase(unittest.TestCase):
       def testSomething(self): pass

   unittest.TextTestRunner().run(MyTestCase())

If the system must be placed into some state before a number of tests are
run, and if that state is certain to be unaffected by the tests, there are
a couple of strategies.

Firstly, each test case could be given a 'setUp' method that lazily sets up
that state, possibly using a helper module.

Secondly, the environment could be set up before the TestRunner is invoked
(or 'unittest.main()' called).

It's worth going to some trouble to make each TestCase outwardly independent
of other code.

Best wishes,

-Steve




Ype Kingma wrote:
> Hello pyunit'ers,
>
> I recently started using unittest.py, and it serves me well.
> At some point I needed to setUp and tearDown a TestSuite.
> The pattern is:
> - bring a system into an interesting state,
> - perform some testcases on the system,
> - bring the system back into it's original state.
> This is useful when setup and/or teardown
> are non trivial and there are more than a few testcases.
>
> I checked the archives a bit but there did not seem to be
> any discussion on this.
>
> So I subclassed SetUpTestSuite from TestSuite. I added methods
> setUpSuite() and tearDownSuite(), called these from the
> __call__() method and allowed for exceptions during setup/teardown
> being reported as test errors.
>
> Having written the code I realised I could have done it by
> implementing a TestCase to execute a TestSuite.
>
> Another look at the code made me realise that it might be added
> into TestSuite without introducing too many backward incompatibilities,
> after all I guess that TestSuite isn't subclassed very often.
>
> The working code is below, comments invited, please use it
> as you see fit.
>
> Ype


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