bpo-38639: Optimize floor(), ceil() and trunc() for floats. (GH-16991)

diff --git a/Lib/test/test_math.py b/Lib/test/test_math.py
index c237bc1..f832246 100644
--- a/Lib/test/test_math.py
+++ b/Lib/test/test_math.py
@@ -240,6 +240,13 @@
     else:
         return None
 
+class FloatLike:
+    def __init__(self, value):
+        self.value = value
+
+    def __float__(self):
+        return self.value
+
 class IntSubclass(int):
     pass
 
@@ -397,12 +404,14 @@
     def testCeil(self):
         self.assertRaises(TypeError, math.ceil)
         self.assertEqual(int, type(math.ceil(0.5)))
-        self.ftest('ceil(0.5)', math.ceil(0.5), 1)
-        self.ftest('ceil(1.0)', math.ceil(1.0), 1)
-        self.ftest('ceil(1.5)', math.ceil(1.5), 2)
-        self.ftest('ceil(-0.5)', math.ceil(-0.5), 0)
-        self.ftest('ceil(-1.0)', math.ceil(-1.0), -1)
-        self.ftest('ceil(-1.5)', math.ceil(-1.5), -1)
+        self.assertEqual(math.ceil(0.5), 1)
+        self.assertEqual(math.ceil(1.0), 1)
+        self.assertEqual(math.ceil(1.5), 2)
+        self.assertEqual(math.ceil(-0.5), 0)
+        self.assertEqual(math.ceil(-1.0), -1)
+        self.assertEqual(math.ceil(-1.5), -1)
+        self.assertEqual(math.ceil(0.0), 0)
+        self.assertEqual(math.ceil(-0.0), 0)
         #self.assertEqual(math.ceil(INF), INF)
         #self.assertEqual(math.ceil(NINF), NINF)
         #self.assertTrue(math.isnan(math.ceil(NAN)))
@@ -410,9 +419,14 @@
         class TestCeil:
             def __ceil__(self):
                 return 42
+        class FloatCeil(float):
+            def __ceil__(self):
+                return 42
         class TestNoCeil:
             pass
-        self.ftest('ceil(TestCeil())', math.ceil(TestCeil()), 42)
+        self.assertEqual(math.ceil(TestCeil()), 42)
+        self.assertEqual(math.ceil(FloatCeil()), 42)
+        self.assertEqual(math.ceil(FloatLike(42.5)), 43)
         self.assertRaises(TypeError, math.ceil, TestNoCeil())
 
         t = TestNoCeil()
@@ -536,16 +550,12 @@
     def testFloor(self):
         self.assertRaises(TypeError, math.floor)
         self.assertEqual(int, type(math.floor(0.5)))
-        self.ftest('floor(0.5)', math.floor(0.5), 0)
-        self.ftest('floor(1.0)', math.floor(1.0), 1)
-        self.ftest('floor(1.5)', math.floor(1.5), 1)
-        self.ftest('floor(-0.5)', math.floor(-0.5), -1)
-        self.ftest('floor(-1.0)', math.floor(-1.0), -1)
-        self.ftest('floor(-1.5)', math.floor(-1.5), -2)
-        # pow() relies on floor() to check for integers
-        # This fails on some platforms - so check it here
-        self.ftest('floor(1.23e167)', math.floor(1.23e167), 1.23e167)
-        self.ftest('floor(-1.23e167)', math.floor(-1.23e167), -1.23e167)
+        self.assertEqual(math.floor(0.5), 0)
+        self.assertEqual(math.floor(1.0), 1)
+        self.assertEqual(math.floor(1.5), 1)
+        self.assertEqual(math.floor(-0.5), -1)
+        self.assertEqual(math.floor(-1.0), -1)
+        self.assertEqual(math.floor(-1.5), -2)
         #self.assertEqual(math.ceil(INF), INF)
         #self.assertEqual(math.ceil(NINF), NINF)
         #self.assertTrue(math.isnan(math.floor(NAN)))
@@ -553,9 +563,14 @@
         class TestFloor:
             def __floor__(self):
                 return 42
+        class FloatFloor(float):
+            def __floor__(self):
+                return 42
         class TestNoFloor:
             pass
-        self.ftest('floor(TestFloor())', math.floor(TestFloor()), 42)
+        self.assertEqual(math.floor(TestFloor()), 42)
+        self.assertEqual(math.floor(FloatFloor()), 42)
+        self.assertEqual(math.floor(FloatLike(41.9)), 41)
         self.assertRaises(TypeError, math.floor, TestNoFloor())
 
         t = TestNoFloor()
@@ -1448,17 +1463,21 @@
         self.assertEqual(math.trunc(-0.999999), -0)
         self.assertEqual(math.trunc(-100.999), -100)
 
-        class TestTrunc(object):
+        class TestTrunc:
             def __trunc__(self):
                 return 23
-
-        class TestNoTrunc(object):
+        class FloatTrunc(float):
+            def __trunc__(self):
+                return 23
+        class TestNoTrunc:
             pass
 
         self.assertEqual(math.trunc(TestTrunc()), 23)
+        self.assertEqual(math.trunc(FloatTrunc()), 23)
 
         self.assertRaises(TypeError, math.trunc)
         self.assertRaises(TypeError, math.trunc, 1, 2)
+        self.assertRaises(TypeError, math.trunc, FloatLike(23.5))
         self.assertRaises(TypeError, math.trunc, TestNoTrunc())
 
     def testIsfinite(self):