cpython/Lib/idlelib/idle_test/test_delegator.py

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import unittest
from idlelib.delegator import Delegator
class DelegatorTest(unittest.TestCase):
def test_mydel(self):
# Test a simple use scenario.
# Initialize an int delegator.
mydel = Delegator(int)
self.assertIs(mydel.delegate, int)
self.assertEqual(mydel._Delegator__cache, set())
# Trying to access a non-attribute of int fails.
self.assertRaises(AttributeError, mydel.__getattr__, 'xyz')
# Add real int attribute 'bit_length' by accessing it.
bl = mydel.bit_length
self.assertIs(bl, int.bit_length)
self.assertIs(mydel.__dict__['bit_length'], int.bit_length)
self.assertEqual(mydel._Delegator__cache, {'bit_length'})
# Add attribute 'numerator'.
mydel.numerator
self.assertEqual(mydel._Delegator__cache, {'bit_length', 'numerator'})
# Delete 'numerator'.
del mydel.numerator
self.assertNotIn('numerator', mydel.__dict__)
# The current implementation leaves it in the name cache.
# self.assertIn('numerator', mydel._Delegator__cache)
# However, this is not required and not part of the specification
# Change delegate to float, first resetting the attributes.
mydel.setdelegate(float) # calls resetcache
self.assertNotIn('bit_length', mydel.__dict__)
self.assertEqual(mydel._Delegator__cache, set())
self.assertIs(mydel.delegate, float)
if __name__ == '__main__':
unittest.main(verbosity=2, exit=2)