diff --git a/Lib/test/test_keywordonlyarg.py b/Lib/test/test_keywordonlyarg.py
new file mode 100644
index 00000000000..0ace785cef6
--- /dev/null
+++ b/Lib/test/test_keywordonlyarg.py
@@ -0,0 +1,151 @@
+#!/usr/bin/env python
+
+"""Unit tests for the keyword only argument specified in PEP 3102."""
+
+__author__ = "Jiwon Seo"
+__email__ = "seojiwon at gmail dot com"
+
+import unittest
+from test.test_support import run_unittest
+
+def posonly_sum(pos_arg1, *arg, **kwarg):
+    return pos_arg1 + sum(arg) + sum(kwarg.values())
+def keywordonly_sum(*, k1=0, k2):
+    return k1 + k2
+def keywordonly_nodefaults_sum(*, k1, k2):
+    return k1 + k2
+def keywordonly_and_kwarg_sum(*, k1, k2, **kwarg):
+    return k1 + k2 + sum(kwarg.values())
+def mixedargs_sum(a, b=0, *arg, k1, k2=0):
+    return a + b + k1 + k2 + sum(arg)
+def mixedargs_sum2(a, b=0, *arg, k1, k2=0, **kwargs):
+    return a + b + k1 + k2 + sum(arg) + sum(kwargs.values())
+
+def sortnum(*nums, reverse=False):
+    return sorted(list(nums), reverse=reverse)
+
+def sortwords(*words, reverse=False, **kwargs):
+    return sorted(list(words), reverse=reverse)
+
+class Foo:
+    def __init__(self, *, k1, k2=0):
+        self.k1 = k1
+        self.k2 = k2
+    def set(self, p1, *, k1, k2):
+        self.k1 = k1
+        self.k2 = k2
+    def sum(self):
+        return self.k1 + self.k2
+
+class KeywordOnlyArgTestCase(unittest.TestCase):
+    def assertRaisesSyntaxError(self, codestr):
+        def shouldRaiseSyntaxError(s):
+            compile(s, "<test>", "single")
+        self.assertRaises(SyntaxError, shouldRaiseSyntaxError, codestr)
+
+    def testSyntaxErrorForFunctionDefinition(self):
+        self.assertRaisesSyntaxError("def f(p, *):\n  pass\n")
+        self.assertRaisesSyntaxError("def f(p1, *, p1=100):\n  pass\n")
+        self.assertRaisesSyntaxError("def f(p1, *k1, k1=100):\n  pass\n")
+        self.assertRaisesSyntaxError("def f(p1, *, k1, k1=100):\n  pass\n")
+        self.assertRaisesSyntaxError("def f(p1, *, k1, **k1):\n  pass\n")
+        self.assertRaisesSyntaxError("def f(p1, *, None, **k1):\n  pass\n")
+        self.assertRaisesSyntaxError("def f(p, *, (k1, k2), **kw):\n  pass\n")
+
+    def testSyntaxForManyArguments(self):
+        fundef = "def f("
+        for i in range(255):
+            fundef += "i%d, "%i
+        fundef += "*, key=100):\n pass\n"
+        self.assertRaisesSyntaxError(fundef)
+
+        fundef2 = "def foo(i,*,"
+        for i in range(255):
+            fundef2 += "i%d, "%i
+        fundef2 += "lastarg):\n  pass\n"
+        self.assertRaisesSyntaxError(fundef2)
+
+        # exactly 255 arguments, should compile ok
+        fundef3 = "def f(i,*,"
+        for i in range(253):
+            fundef3 += "i%d, "%i
+        fundef3 += "lastarg):\n  pass\n"
+        compile(fundef3, "<test>", "single")
+ 
+    def testSyntaxErrorForFunctionCall(self):
+        self.assertRaisesSyntaxError("f(p, k=1, p2)")
+        self.assertRaisesSyntaxError("f(p, *(1,2), k1=100)")
+
+    def testRaiseErrorFuncallWithUnexpectedKeywordArgument(self):
+        self.assertRaises(TypeError, keywordonly_sum, ())
+        self.assertRaises(TypeError, keywordonly_nodefaults_sum, ())
+        self.assertRaises(TypeError, Foo, ())
+        try:
+            keywordonly_sum(k2=100, non_existing_arg=200)
+            self.fail("should raise TypeError")
+        except TypeError:
+            pass
+        try:
+            keywordonly_nodefaults_sum(k2=2)
+            self.fail("should raise TypeError")
+        except TypeError:
+            pass
+
+    def testFunctionCall(self):
+        self.assertEquals(1, posonly_sum(1))
+        self.assertEquals(1+2, posonly_sum(1,**{"2":2}))
+        self.assertEquals(1+2+3, posonly_sum(1,*(2,3)))
+        self.assertEquals(1+2+3+4, posonly_sum(1,*(2,3),**{"4":4}))
+
+        self.assertEquals(1, keywordonly_sum(k2=1))
+        self.assertEquals(1+2, keywordonly_sum(k1=1, k2=2))
+
+        self.assertEquals(1+2, keywordonly_and_kwarg_sum(k1=1, k2=2))
+        self.assertEquals(1+2+3, keywordonly_and_kwarg_sum(k1=1, k2=2, k3=3))
+        self.assertEquals(1+2+3+4,
+                          keywordonly_and_kwarg_sum(k1=1, k2=2,
+                                                    **{"a":3,"b":4}))
+
+        self.assertEquals(1+2, mixedargs_sum(1, k1=2))
+        self.assertEquals(1+2+3, mixedargs_sum(1, 2, k1=3))
+        self.assertEquals(1+2+3+4, mixedargs_sum(1, 2, k1=3, k2=4))
+        self.assertEquals(1+2+3+4+5, mixedargs_sum(1, 2, 3, k1=4, k2=5))
+
+        self.assertEquals(1+2, mixedargs_sum2(1, k1=2))
+        self.assertEquals(1+2+3, mixedargs_sum2(1, 2, k1=3))
+        self.assertEquals(1+2+3+4, mixedargs_sum2(1, 2, k1=3, k2=4))
+        self.assertEquals(1+2+3+4+5, mixedargs_sum2(1, 2, 3, k1=4, k2=5))
+        self.assertEquals(1+2+3+4+5+6,
+                          mixedargs_sum2(1, 2, 3, k1=4, k2=5, k3=6))
+        self.assertEquals(1+2+3+4+5+6,
+                          mixedargs_sum2(1, 2, 3, k1=4, **{'k2':5, 'k3':6}))
+
+        self.assertEquals(1, Foo(k1=1).sum())
+        self.assertEquals(1+2, Foo(k1=1,k2=2).sum())
+
+        self.assertEquals([1,2,3], sortnum(3,2,1))
+        self.assertEquals([3,2,1], sortnum(1,2,3, reverse=True))
+
+        self.assertEquals(['a','b','c'], sortwords('a','c','b'))
+        self.assertEquals(['c','b','a'], sortwords('a','c','b', reverse=True))
+        self.assertEquals(['c','b','a'],
+                          sortwords('a','c','b', reverse=True, ignore='ignore'))
+
+    def testKwDefaults(self):
+        def foo(p1,p2=0, *, k1, k2=0):
+            return p1 + p2 + k1 + k2
+
+        self.assertEquals(2, foo.func_code.co_kwonlyargcount)
+        self.assertEquals({"k2":0}, foo.func_kwdefaults)
+        foo.func_kwdefaults = {"k1":0}
+        try:
+            foo(1,k1=10)
+            self.fail("func_kwdefaults is not properly changed")
+        except TypeError:
+            pass
+
+def test_main():
+    run_unittest(KeywordOnlyArgTestCase)
+
+if __name__ == "__main__":
+    test_main()