[unittest] Run setUp only once

[Jean-Paul Calderone]

On Tue, 29 Jul 2008 19:26:09 +0200, Nikolaus Rath <nikolaus at rath.org> wrote:
>Jean-Paul Calderone <exarkun at divmod.com> writes:
>> On Tue, 29 Jul 2008 16:35:55 +0200, Nikolaus Rath <nikolaus at rath.org> wrote:
>>>Hello,
>>>
>>>I have a number of conceptually separate tests that nevertheless need
>>>a common, complicated and expensive setup.
>>>
>>>Unfortunately, unittest runs the setUp method once for each defined
>>>test, even if they're part of the same class as in
>>>
>>>class TwoTests(unittest.TestCase):
>>>    def setUp(self):
>>>        # do something very time consuming
>>>
>>>    def testOneThing(self):
>>>
>>>
>>>    def testADifferentThing(self):
>>>
>>>
>>>which would call setUp twice.
>>>
>>>
>>>Is there any way to avoid this, without packing all the unrelated
>>>tests into one big function?
>>>
>>
>>    class TwoTests(unittest.TestCase):
>>        setUpResult = None
>>
>>        def setUp(self):
>>            if self.setUpResult is None:
>>                self.setUpResult = computeIt()
>>
>>        ...
>>
>> There are plenty of variations on this pattern.
>
>
>But at least this variation doesn't work, because unittest apparently
>also creates two separate TwoTests instances for the two tests. Isn't
>there some way to convince unittest to reuse the same instance instead
>of trying to solve the problem in the test code itself?
>

Eh sorry, you're right, the above is broken.  `setUpResult` should be
a class attribute instead of an instance attribute.

Jean-Paul