redo on top of python#121071

Author: skirpichev

Lib/test/test_float.py

@@ -863,29 +863,7 @@ def test_short_repr(self):
             self.assertEqual(repr(float(negs)), str(float(negs)))
 
 @support.requires_IEEE_754
-class RoundTestCase(unittest.TestCase):
-
-    def assertFloatsAreIdentical(self, x, y):
-        """Fail unless floats x and y are identical, in the sense that:
-        (1) both x and y are nans, or
-        (2) both x and y are infinities, with the same sign, or
-        (3) both x and y are zeros, with the same sign, or
-        (4) x and y are both finite and nonzero, and x == y
-        """
-        msg = 'floats {!r} and {!r} are not identical'
-
-        if isnan(x) or isnan(y):
-            if isnan(x) and isnan(y):
-                return
-        elif x == y:
-            if x != 0.0:
-                return
-            # both zero; check that signs match
-            elif copysign(1.0, x) == copysign(1.0, y):
-                return
-            else:
-                msg += ': zeros have different signs'
-        self.fail(msg.format(x, y))
+class RoundTestCase(unittest.TestCase, FloatsAreIdenticalMixin):
 
     def test_inf_nan(self):
         self.assertRaises(OverflowError, round, INF)