test.support: add requires_mac_ver() function

Add also linux_version() to __all__.

Lib/test/support.py

@@ -37,7 +37,8 @@ __all__ = [
     "Error", "TestFailed", "ResourceDenied", "import_module",
     "verbose", "use_resources", "max_memuse", "record_original_stdout",
     "get_original_stdout", "unload", "unlink", "rmtree", "forget",
-    "is_resource_enabled", "requires", "find_unused_port", "bind_port",
+    "is_resource_enabled", "requires", "linux_version", "requires_mac_ver",
+    "find_unused_port", "bind_port",
     "IPV6_ENABLED", "is_jython", "TESTFN", "HOST", "SAVEDCWD", "temp_cwd",
     "findfile", "sortdict", "check_syntax_error", "open_urlresource",
     "check_warnings", "CleanImport", "EnvironmentVarGuard", "TransientResource",
@@ -299,6 +300,25 @@ def linux_version():
     except ValueError:
         return 0, 0, 0
 
+def requires_mac_ver(*min_version):
+    """Raise SkipTest if the OS is Mac OS X and the OS X version if less than
+    min_version.
+
+    For example, support.requires_linux_version(10, 5) raises SkipTest if the
+    version is less than 10.5.
+    """
+    if sys.platform != 'darwin':
+        return
+    version_txt = platform.mac_ver()[0]
+    try:
+        version = tuple(map(int, version_txt.split('.')))
+    except ValueError:
+        return
+    if version < min_version:
+        min_version_txt = '.'.join(map(str, min_version))
+        raise unittest.SkipTest("Mac OS X %s or higher required, not %s"
+                                % (min_version_txt, version_txt))
+
 HOST = 'localhost'
 
 def find_unused_port(family=socket.AF_INET, socktype=socket.SOCK_STREAM):

Lib/test/test_math.py

@@ -2,6 +2,7 @@
 # XXXX Should not do tests around zero only
 
 from test.support import run_unittest, verbose, requires_IEEE_754
+from test import support
 import unittest
 import math
 import os
@@ -669,10 +670,10 @@ class MathTests(unittest.TestCase):
         self.assertTrue(math.isnan(math.log2(NAN)))
 
     @requires_IEEE_754
-    @unittest.skipIf(sys.platform == 'darwin'
-                     and platform.mac_ver()[0].startswith('10.4.'),
-                     'Mac OS X Tiger log2() is not accurate enough')
     def testLog2Exact(self):
+        # log2() is not accurate enough on Mac OS X Tiger (10.4)
+        support.requires_mac_ver(10, 5)
+
         # Check that we get exact equality for log2 of powers of 2.
         actual = [math.log2(math.ldexp(1.0, n)) for n in range(-1074, 1024)]
         expected = [float(n) for n in range(-1074, 1024)]