Strengthen BytesWarning tests.

Lib/test/test_bytes.py

@@ -9,15 +9,28 @@ import os
 import re
 import sys
 import copy
-import operator
+import functools
 import pickle
 import tempfile
 import unittest
-import warnings
 import test.support
 import test.string_tests
 import test.buffer_tests
 
+
+if sys.flags.bytes_warning:
+    def check_bytes_warnings(func):
+        @functools.wraps(func)
+        def wrapper(*args, **kw):
+            with test.support.check_warnings(('', BytesWarning)):
+                return func(*args, **kw)
+        return wrapper
+else:
+    # no-op
+    def check_bytes_warnings(func):
+        return func
+
+
 class Indexable:
     def __init__(self, value=0):
         self.value = value
@@ -121,9 +134,8 @@ class BaseBytesTest(unittest.TestCase):
         self.assertFalse(b3 <  b2)
         self.assertFalse(b3 <= b2)
 
+    @check_bytes_warnings
     def test_compare_to_str(self):
-        with test.support.check_warnings():
-            warnings.simplefilter('ignore', BytesWarning)
         # Byte comparisons with unicode should always fail!
         # Test this for all expected byte orders and Unicode character
         # sizes.
@@ -823,9 +835,8 @@ class AssortedBytesTest(unittest.TestCase):
     # Test various combinations of bytes and bytearray
     #
 
+    @check_bytes_warnings
     def test_repr_str(self):
-        with test.support.check_warnings():
-            warnings.simplefilter('ignore', BytesWarning)
         for f in str, repr:
             self.assertEqual(f(bytearray()), "bytearray(b'')")
             self.assertEqual(f(bytearray([0])), "bytearray(b'\\x00')")
@@ -876,9 +887,8 @@ class AssortedBytesTest(unittest.TestCase):
         b = bytearray(buf)
         self.assertEqual(b, bytearray(sample))
 
+    @check_bytes_warnings
     def test_to_str(self):
-        with test.support.check_warnings():
-            warnings.simplefilter('ignore', BytesWarning)
         self.assertEqual(str(b''), "b''")
         self.assertEqual(str(b'x'), "b'x'")
         self.assertEqual(str(b'\x80'), "b'\\x80'")
@@ -930,19 +940,18 @@ class AssortedBytesTest(unittest.TestCase):
 
     def test_compare(self):
         if sys.flags.bytes_warning:
-            with test.support.check_warnings():
-                warnings.simplefilter('error', BytesWarning)
-                with self.assertRaises(BytesWarning):
+            def bytes_warning():
+                return test.support.check_warnings(('', BytesWarning))
+            with bytes_warning():
                 b'' == ''
-                with self.assertRaises(BytesWarning):
+            with bytes_warning():
                 b'' != ''
-                with self.assertRaises(BytesWarning):
+            with bytes_warning():
                 bytearray(b'') == ''
-                with self.assertRaises(BytesWarning):
+            with bytes_warning():
                 bytearray(b'') != ''
         else:
-            # self.skipTest("BytesWarning is needed for this test: use -bb option")
-            pass
+            self.skipTest("BytesWarning is needed for this test: use -bb option")
 
     # Optimizations:
     # __iter__? (optimization)