Example of a unit test for a list-flattening function

flatten.py

import types 
import unittest

def flatten(input, list=[]):
    if isinstance(input, types.ListType):
        for item in input:
            flatten(item, list)
    else:
        list = list.append(input)
    return list

class TestFlatten(unittest.TestCase):
    def testFlattenMethod(self):
        INPUT=[[1,2,[3],4,[5,[6,7,8]]]]
        EXPECTED_OUTPUT=[1,2,3,4,5,6,7,8]

        ACTUAL_OUTPUT=flatten(INPUT);
        #print "EXPECTED_OUTPUT", EXPECTED_OUTPUT
        #print "ACTUAL_OUTPUT", ACTUAL_OUTPUT
        self.assertTrue(EXPECTED_OUTPUT, ACTUAL_OUTPUT)

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