Test round-trip on float.as_integer_ratio() and float.__truediv__().

Lib/test/test_builtin.py

@@ -697,6 +697,12 @@ class BuiltinTest(unittest.TestCase):
             ]:
             self.assertEqual(f.as_integer_ratio(), ratio)
 
+        for i in range(10000):
+            f = random.random()
+            f *= 10 ** random.randint(-100, 100)
+            n, d = f.as_integer_ratio()
+            self.assertEqual(float(n).__truediv__(d), f)
+
         R = rational.Rational
         self.assertEqual(R(0, 1),
                          R(*float(0.0).as_integer_ratio()))