Method check_truediv

Lib/test/test_long.py:843–871

Verify that the result of a/b is correctly rounded, by comparing it with a pure Python implementation of correctly rounded division. b should be nonzero.

(self, a, b, skip_small=True)

        self.assertEqual(12 // 3, 4)

    def check_truediv(self, a, b, skip_small=True):
        """Verify that the result of a/b is correctly rounded, by
        comparing it with a pure Python implementation of correctly
        rounded division.  b should be nonzero."""

        # skip check for small a and b: in this case, the current
        # implementation converts the arguments to float directly and
        # then applies a float division.  This can give doubly-rounded
        # results on x87-using machines (particularly 32-bit Linux).
        if skip_small and max(abs(a), abs(b)) < 2**DBL_MANT_DIG:
            return

        try:
            # use repr so that we can distinguish between -0.0 and 0.0
            expected = repr(truediv(a, b))
        except OverflowError:
            expected = 'overflow'
        except ZeroDivisionError:
            expected = 'zerodivision'

        try:
            got = repr(a / b)
        except OverflowError:
            got = 'overflow'
        except ZeroDivisionError:
            got = 'zerodivision'

        self.assertEqual(expected, got, "Incorrectly rounded division {}/{}: "
                         "expected {}, got {}".format(a, b, expected, got))

    @unittest.expectedFailure  # TODO: RUSTPYTHON
    @support.requires_IEEE_754