1 files changed, 47 insertions, 8 deletions

diff --git a/Lib/test/test_decimal.py b/Lib/test/test_decimal.py
index 4071eff8db..c2a6b0e007 100644
--- a/Lib/test/test_decimal.py
+++ b/Lib/test/test_decimal.py
@@ -26,6 +26,7 @@ with the corresponding argument.
 
 import math
 import os, sys
+import operator
 import pickle, copy
 import unittest
 from decimal import *
@@ -1080,18 +1081,56 @@ class DecimalArithmeticOperatorsTest(unittest.TestCase):
         self.assertEqual(abs(Decimal(45)), abs(Decimal(-45)))  # abs
 
     def test_nan_comparisons(self):
+        # comparisons involving signaling nans signal InvalidOperation
+
+        # order comparisons (<, <=, >, >=) involving only quiet nans
+        # also signal InvalidOperation
+
+        # equality comparisons (==, !=) involving only quiet nans
+        # don't signal, but return False or True respectively.
+
         n = Decimal('NaN')
         s = Decimal('sNaN')
         i = Decimal('Inf')
         f = Decimal('2')
-        for x, y in [(n, n), (n, i), (i, n), (n, f), (f, n),
-                     (s, n), (n, s), (s, i), (i, s), (s, f), (f, s), (s, s)]:
-            self.assertTrue(x != y)
-            self.assertTrue(not (x == y))
-            self.assertTrue(not (x < y))
-            self.assertTrue(not (x <= y))
-            self.assertTrue(not (x > y))
-            self.assertTrue(not (x >= y))
+
+        qnan_pairs = (n, n), (n, i), (i, n), (n, f), (f, n)
+        snan_pairs = (s, n), (n, s), (s, i), (i, s), (s, f), (f, s), (s, s)
+        order_ops = operator.lt, operator.le, operator.gt, operator.ge
+        equality_ops = operator.eq, operator.ne
+
+        # results when InvalidOperation is not trapped
+        for x, y in qnan_pairs + snan_pairs:
+            for op in order_ops + equality_ops:
+                got = op(x, y)
+                expected = True if op is operator.ne else False
+                self.assertIs(expected, got,
+                              "expected {0!r} for operator.{1}({2!r}, {3!r}); "
+                              "got {4!r}".format(
+                        expected, op.__name__, x, y, got))
+
+        # repeat the above, but this time trap the InvalidOperation
+        with localcontext() as ctx:
+            ctx.traps[InvalidOperation] = 1
+
+            for x, y in qnan_pairs:
+                for op in equality_ops:
+                    got = op(x, y)
+                    expected = True if op is operator.ne else False
+                    self.assertIs(expected, got,
+                                  "expected {0!r} for "
+                                  "operator.{1}({2!r}, {3!r}); "
+                                  "got {4!r}".format(
+                            expected, op.__name__, x, y, got))
+
+            for x, y in snan_pairs:
+                for op in equality_ops:
+                    self.assertRaises(InvalidOperation, operator.eq, x, y)
+                    self.assertRaises(InvalidOperation, operator.ne, x, y)
+
+            for x, y in qnan_pairs + snan_pairs:
+                for op in order_ops:
+                    self.assertRaises(InvalidOperation, op, x, y)
 
     def test_copy_sign(self):
         d = Decimal(1).copy_sign(Decimal(-2))