diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index 7384999..1be1b71 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -5,10 +5,10 @@
 
 import io
 
-
-class MockReadIO(io.RawIOBase):
-    def __init__(self, readStack):
+class MockIO(io.RawIOBase):
+    def __init__(self, readStack=()):
         self._readStack = list(readStack)
+        self._writeStack = []
 
     def read(self, n=None):
         try:
@@ -16,27 +16,41 @@
         except:
             return io.EOF
 
+    def write(self, b):
+        self._writeStack.append(b)
+        return len(b)
+
+    def writable(self):
+        return True
+
     def fileno(self):
         return 42
 
     def readable(self):
         return True
 
-
-class MockWriteIO(io.RawIOBase):
-    def __init__(self):
-        self._writeStack = []
-
-    def write(self, b):
-        self._writeStack.append(b)
-        return len(b)
-
-    def writeable(self):
+    def seekable(self):
         return True
 
-    def fileno(self):
+    def seek(self, pos, whence):
+        pass
+
+    def tell(self):
         return 42
 
+class MockNonBlockWriterIO(io.RawIOBase):
+    def __init__(self, blockingScript):
+        self.bs = list(blockingScript)
+        self._write_stack = []
+    def write(self, b):
+        self._write_stack.append(b)
+        n = self.bs.pop(0)
+        if (n < 0):
+            raise io.BlockingIO(0, "test blocking", -n)
+        else:
+            return n
+    def writable(self):
+        return True
 
 class IOTest(unittest.TestCase):
 
@@ -90,9 +104,7 @@
         f = io.BytesIO(data)
         self.read_ops(f)
 
-
 class BytesIOTest(unittest.TestCase):
-
     def testInit(self):
         buf = b"1234567890"
         bytesIo = io.BytesIO(buf)
@@ -134,44 +146,51 @@
         bytesIo.seek(10000)
         self.assertEquals(10000, bytesIo.tell())
 
-
 class BufferedReaderTest(unittest.TestCase):
-
     def testRead(self):
-        rawIo = MockReadIO((b"abc", b"d", b"efg"))
+        rawIo = MockIO((b"abc", b"d", b"efg"))
         bufIo = io.BufferedReader(rawIo)
 
         self.assertEquals(b"abcdef", bufIo.read(6))
 
+    def testReadNonBlocking(self):
+        # Inject some None's in there to simulate EWOULDBLOCK
+        rawIo = MockIO((b"abc", b"d", None, b"efg", None, None))
+        bufIo = io.BufferedReader(rawIo)
+
+        self.assertEquals(b"abcd", bufIo.read(6))
+        self.assertEquals(b"e", bufIo.read(1))
+        self.assertEquals(b"fg", bufIo.read())
+        self.assert_(None is bufIo.read())
+        self.assertEquals(io.EOF, bufIo.read())
+
     def testReadToEof(self):
-        rawIo = MockReadIO((b"abc", b"d", b"efg"))
+        rawIo = MockIO((b"abc", b"d", b"efg"))
         bufIo = io.BufferedReader(rawIo)
 
         self.assertEquals(b"abcdefg", bufIo.read(9000))
 
     def testReadNoArgs(self):
-        rawIo = MockReadIO((b"abc", b"d", b"efg"))
+        rawIo = MockIO((b"abc", b"d", b"efg"))
         bufIo = io.BufferedReader(rawIo)
 
         self.assertEquals(b"abcdefg", bufIo.read())
 
     def testFileno(self):
-        rawIo = MockReadIO((b"abc", b"d", b"efg"))
+        rawIo = MockIO((b"abc", b"d", b"efg"))
         bufIo = io.BufferedReader(rawIo)
 
         self.assertEquals(42, bufIo.fileno())
 
     def testFilenoNoFileno(self):
-        # TODO will we always have fileno() function? If so, kill
+        # XXX will we always have fileno() function? If so, kill
         # this test. Else, write it.
         pass
 
-
 class BufferedWriterTest(unittest.TestCase):
-
     def testWrite(self):
         # Write to the buffered IO but don't overflow the buffer.
-        writer = MockWriteIO()
+        writer = MockIO()
         bufIo = io.BufferedWriter(writer, 8)
 
         bufIo.write(b"abc")
@@ -179,7 +198,7 @@
         self.assertFalse(writer._writeStack)
 
     def testWriteOverflow(self):
-        writer = MockWriteIO()
+        writer = MockIO()
         bufIo = io.BufferedWriter(writer, 8)
 
         bufIo.write(b"abc")
@@ -187,8 +206,33 @@
 
         self.assertEquals(b"abcdefghijkl", writer._writeStack[0])
 
+    def testWriteNonBlocking(self):
+        raw = MockNonBlockWriterIO((9, 2, 22, -6, 10, 12, 12))
+        bufIo = io.BufferedWriter(raw, 8, 16)
+
+        bufIo.write(b"asdf")
+        bufIo.write(b"asdfa")
+        self.assertEquals(b"asdfasdfa", raw._write_stack[0])
+
+        bufIo.write(b"asdfasdfasdf")
+        self.assertEquals(b"asdfasdfasdf", raw._write_stack[1])
+        bufIo.write(b"asdfasdfasdf")
+        self.assertEquals(b"dfasdfasdf", raw._write_stack[2])
+        self.assertEquals(b"asdfasdfasdf", raw._write_stack[3])
+
+        bufIo.write(b"asdfasdfasdf")
+
+        # XXX I don't like this test. It relies too heavily on how the algorithm
+        # actually works, which we might change. Refactor later.
+
+    def testFileno(self):
+        rawIo = MockIO((b"abc", b"d", b"efg"))
+        bufIo = io.BufferedWriter(rawIo)
+
+        self.assertEquals(42, bufIo.fileno())
+
     def testFlush(self):
-        writer = MockWriteIO()
+        writer = MockIO()
         bufIo = io.BufferedWriter(writer, 8)
 
         bufIo.write(b"abc")
@@ -196,11 +240,51 @@
 
         self.assertEquals(b"abc", writer._writeStack[0])
 
-# TODO. Tests for open()
+class BufferedRWPairTest(unittest.TestCase):
+    def testRWPair(self):
+        r = MockIO(())
+        w = MockIO()
+        pair = io.BufferedRWPair(r, w)
+
+        # XXX need implementation
+
+class BufferedRandom(unittest.TestCase):
+    def testReadAndWrite(self):
+        raw = MockIO((b"asdf", b"ghjk"))
+        rw = io.BufferedRandom(raw, 8, 12)
+
+        self.assertEqual(b"as", rw.read(2))
+        rw.write(b"ddd")
+        rw.write(b"eee")
+        self.assertFalse(raw._writeStack) # Buffer writes
+        self.assertEqual(b"ghjk", rw.read()) # This read forces write flush
+        self.assertEquals(b"dddeee", raw._writeStack[0])
+
+    def testSeekAndTell(self):
+        raw = io.BytesIO(b"asdfghjkl")
+        rw = io.BufferedRandom(raw)
+
+        self.assertEquals(b"as", rw.read(2))
+        self.assertEquals(2, rw.tell())
+        rw.seek(0, 0)
+        self.assertEquals(b"asdf", rw.read(4))
+
+        rw.write(b"asdf")
+        rw.seek(0, 0)
+        self.assertEquals(b"asdfasdfl", rw.read())
+        self.assertEquals(9, rw.tell())
+        rw.seek(-4, 2)
+        self.assertEquals(5, rw.tell())
+        rw.seek(2, 1)
+        self.assertEquals(7, rw.tell())
+        self.assertEquals(b"fl", rw.read(11))
+
+# XXX Tests for open()
 
 def test_main():
     test_support.run_unittest(IOTest, BytesIOTest, BufferedReaderTest,
-                              BufferedWriterTest)
+                              BufferedWriterTest, BufferedRWPairTest,
+                              BufferedRandom)
 
 if __name__ == "__main__":
     test_main()