Question

I’m trying to write unit tests to ensure correctness of various decorators I’ve written. Here’s the start of the code I’m trying to write:

import unittest

from memoizer import Memoizer
from strategies.mru import MRU


@Memoizer(strategy=MRU(maxsize=10))
def fib(x):
  if x < 2:
    return 1
  else:
    return fib(x-1) + fib(x-2)


class TestMemoizer(unittest.TestCase):

  def test_simple(self):
    self.assertEqual(fib(0), 1)
    self.assertEqual(fib(1), 1)
    self.assertEqual(fib(10), 89)


if __name__ == '__main__':
  unittest.main()

While this works decently for the MRU strategy I have above, I plan to write additional strategies, in which case I’ll need to decorate with the fib function in different ways. (Recall that because fib calls fib, setting fib2 = memoize(fib) does not memoize intermediate values so that will not work.) What is the correct way to test the other decorators?

Answer 1

Take a look at the tests in the standard library for examples: http://hg.python.org/cpython/file/3.2/Lib/test/test_functools.py#l553

I usually add some instrumentation to the function being wrapped so that I can monitor the calls.

Instead of memoizing the test function at the module level, I create the memoized function inside the test so that a new one is created for each test and for each decorator variant.