Question

I currently have a unittest.TestCase that looks like..

class test_appletrailer(unittest.TestCase):     def setup(self):         self.all_trailers = Trailers(res = '720', verbose = True)      def test_has_trailers(self):         self.failUnless(len(self.all_trailers) > 1)      # ..more tests.. 

This works fine, but the Trailers() call takes about 2 seconds to run.. Given that setUp() is called before each test is run, the tests now take almost 10 seconds to run (with only 3 test functions)

What is the correct way of caching the self.all_trailers variable between tests?

Removing the setUp function, and doing..

class test_appletrailer(unittest.TestCase):     all_trailers = Trailers(res = '720', verbose = True) 

..works, but then it claims ‘Ran 3 tests in 0.000s’ which is incorrect.. The only other way I could think of is to have a cache_trailers global variable (which works correctly, but is rather horrible):

cache_trailers = None class test_appletrailer(unittest.TestCase):     def setUp(self):         global cache_trailers         if cache_trailers is None:             cache_trailers = self.all_trailers = all_trailers = Trailers(res = '720', verbose = True)         else:             self.all_trailers = cache_trailers 

Answer 1

How about using a class member that only gets initialized once?

class test_appletrailer(unittest.TestCase):      all_trailers = None      def setup(self):         # Only initialize all_trailers once.         if self.all_trailers is None:             self.__class__.all_trailers = Trailers(res = '720', verbose = True) 

Lookups that refer to self.all_trailers will go to the next step in the MRO — self.__class__.all_trailers, which will be initialized.