python - test initialization of object and use it -

i have class , want test built in unittest module. in particular want test if can create intances without throwing errors , if can use them.

the problem creation of objects quite slow, can create object in setupclass method , reuse them.

@classmethod def setupclass(cls):     cls.obj = myclass(argument)  def testconstruction(self):     obj = myclass(argument)  def test1(self):     self.assertequal(self.obj.metohd1(), 1) 

the point is

1. i creating 2 times expensive object
2. setup calles before testconstruction, cannot check failure inside testconstruction

i happy example if there way set testconstruction executed before other tests.

why not test both initialization , functionality in same test?

class mytestcase(testcase):     def test_complicated_object(self):         obj = myclass(argument)         self.assertequal(obj.method(), 1) 

alternatively, can have 1 test case object initialization, , 1 test case other tests. mean have create object twice, might acceptable tradeoff:

class creationtestcase(testcase):     def test_complicated_object(self):         obj = myclass(argument)  class usagetestcase(testcase):     @classmethod     def setupclass(cls):         cls.obj = myclass(argument)      def test_complicated_object(self):         self.assertequal(obj.method(), 1) 

do note if methods mutate object, you're going trouble.

alternatively, can this, again, wouldn't recommend it

class mytestcase(testcase):     _test_object = none      @classmethod     def _create_test_object(cls):         if cls._test_object none:             cls._test_object = myclass(argument)         return cls._test_object      def test_complicated_object(self):         obj = self._create_test_object()         self.assertequal(obj.method(), 1)      def more_test(self):         obj = self._create_test_object()         # obj cached, unless creation failed