diff options
Diffstat (limited to 'Lib/test/test_long.py')
| -rw-r--r-- | Lib/test/test_long.py | 11 |
1 files changed, 11 insertions, 0 deletions
diff --git a/Lib/test/test_long.py b/Lib/test/test_long.py index 3c8e9e22e17..f2a622b5868 100644 --- a/Lib/test/test_long.py +++ b/Lib/test/test_long.py @@ -1502,6 +1502,17 @@ class LongTest(unittest.TestCase): self.assertEqual(type(numerator), int) self.assertEqual(type(denominator), int) + def test_square(self): + # Multiplication makes a special case of multiplying an int with + # itself, using a special, faster algorithm. This test is mostly + # to ensure that no asserts in the implementation trigger, in + # cases with a maximal amount of carries. + for bitlen in range(1, 400): + n = (1 << bitlen) - 1 # solid string of 1 bits + with self.subTest(bitlen=bitlen, n=n): + # (2**i - 1)**2 = 2**(2*i) - 2*2**i + 1 + self.assertEqual(n**2, + (1 << (2 * bitlen)) - (1 << (bitlen + 1)) + 1) if __name__ == "__main__": unittest.main() |