diff -r f00c1b696e86 Lib/test/regrtest.py
--- a/Lib/test/regrtest.py	Mon Jan 24 19:19:01 2011 +0100
+++ b/Lib/test/regrtest.py	Wed Jan 26 23:58:38 2011 +0100
@@ -42,6 +42,9 @@
                 -- specify which special resource intensive tests to run
 -M/--memlimit LIMIT
                 -- run very large memory-consuming tests
+   --testdir DIR
+                -- execute test files in the specified directory (instead
+                   of the Python stdlib test suite)
 
 Special runs
 
@@ -265,7 +268,7 @@
              'use=', 'threshold=', 'trace', 'coverdir=', 'nocoverdir',
              'runleaks', 'huntrleaks=', 'memlimit=', 'randseed=',
              'multiprocess=', 'coverage', 'slaveargs=', 'forever', 'debug',
-             'start=', 'nowindows', 'header'])
+             'start=', 'nowindows', 'header', 'testdir='])
     except getopt.error as msg:
         usage(msg)
 
@@ -386,6 +389,14 @@
             print()   # Force a newline (just in case)
             print(json.dumps(result))
             sys.exit(0)
+        elif o == '--testdir':
+            # CWD is replaced with a temporary dir before calling main(), so we
+            # need to check if it's a relative path, and join it with the
+            # saved CWD
+            if os.path.isabs(a):
+                testdir = a
+            else:
+                testdir = os.path.join(support.SAVEDCWD, a)
         else:
             print(("No handler for option {}.  Please report this as a bug "
                    "at http://bugs.python.org.").format(o), file=sys.stderr)