diff --git a/Lib/timeit.py b/Lib/timeit.py
index 5c613fc..8e04645 100644
--- a/Lib/timeit.py
+++ b/Lib/timeit.py
@@ -232,10 +232,10 @@
     """Convenience function to create Timer object and call repeat method."""
     return Timer(stmt, setup, timer).repeat(repeat, number)
 
-def main(args=None):
+def main(args=None, *, _wrap_timer=None):
     """Main program, used when run as a script.
 
-    The optional argument specifies the command line to be parsed,
+    The optional 'args' argument specifies the command line to be parsed,
     defaulting to sys.argv[1:].
 
     The return value is an exit code to be passed to sys.exit(); it
@@ -244,6 +244,10 @@
     When an exception happens during timing, a traceback is printed to
     stderr and the return value is 1.  Exceptions at other times
     (including the template compilation) are not caught.
+
+    '_wrap_timer' is an internal interface used for unit testing.  If it
+    is not None, it must be a callable that accepts a timer function
+    and returns another timer function (used for unit testing).
     """
     if args is None:
         args = sys.argv[1:]
@@ -289,6 +293,8 @@
     # directory)
     import os
     sys.path.insert(0, os.curdir)
+    if _wrap_timer is not None:
+        timer = _wrap_timer(timer)
     t = Timer(stmt, setup, timer)
     if number == 0:
         # determine number so that 0.2 <= total time < 2.0