Revert r61508: it caused test_mailbox to fail on all platforms.
diff --git a/Lib/test/test_io.py b/Lib/test/test_io.py
index 27814a0..49404e1 100644
--- a/Lib/test/test_io.py
+++ b/Lib/test/test_io.py
@@ -590,9 +590,7 @@
         # I=0, O=3
         (b'i.o3.x.xyz.toolong.', False, 'x--.xyz.too.'),
         # I=6, O=3
-        (b'i.o3.i6.abcdefghijklmnop', True, 'abc.ghi.mno.'),
-        # I=5, O=8 with newlines
-        (b'i.o8.i5.abc\ndef\nghy\nz', True, 'abc\nd---.ef\ngh---.y\nz-----.')
+        (b'i.o3.i6.abcdefghijklmnop', True, 'abc.ghi.mno.')
     ]
 
     def testDecoder(self):
@@ -892,8 +890,8 @@
                 return codecs.CodecInfo(
                     name='test_decoder', encode=None, decode=None,
                     incrementalencoder=None,
-                    incrementaldecoder=StatefulIncrementalDecoder,
-                    streamreader=None, streamwriter=None)
+                    streamreader=None, streamwriter=None,
+                    incrementaldecoder=StatefulIncrementalDecoder)
 
         def testSeekAndTellWithData(data, min_pos=0):
             """Tell/seek to various points within a data stream and ensure
@@ -905,42 +903,16 @@
             decoded = f.read()
             f.close()
 
-            # Use read() to move to various positions in the input;
-            # then tell, read some more data, and seek back.
-            for i in range(min_pos, len(decoded) + 1): # to read before tell
-                for j in [1, 5, len(decoded)]: # to read after tell
+            for i in range(min_pos, len(decoded) + 1): # seek positions
+                for j in [1, 5, len(decoded) - i]: # read lengths
                     f = io.open(test_support.TESTFN, encoding='test_decoder')
                     self.assertEquals(f.read(i), decoded[:i])
                     cookie = f.tell()
                     self.assertEquals(f.read(j), decoded[i:i + j])
                     f.seek(cookie)
-                    self.assertEquals(f.tell(), cookie)
                     self.assertEquals(f.read(), decoded[i:])
                     f.close()
 
-            lines = len(decoded.split('\n'))
-
-            # Use readline() to move to various positions in the input;
-            # then tell, read some more data, and seek back.
-            for limit in [-1, 4, 128]: # 'limit' argument for readline()
-                for j in [1, 5, len(decoded)]: # to read after tell()
-                    f = io.open(test_support.TESTFN, encoding='test_decoder')
-                    text = ''
-                    for k in range(lines): # repeatedly call readline()
-                        line = f.readline(limit=limit)
-                        if limit >= 0:
-                            self.assert_(len(line) <= limit)
-                        text += line
-                        i = len(text)
-                        self.assertEquals(text, decoded[:i])
-                        cookie = f.tell()
-                        self.assertEquals(f.read(j), decoded[i:i + j])
-                        f.seek(cookie)
-                        self.assertEquals(f.tell(), cookie)
-                        self.assertEquals(f.read(), decoded[i:])
-                        f.seek(cookie)
-                    f.close()
-
         # Register a special incremental decoder for testing.
         codecs.register(lookupTestDecoder)
         self.codecEnabled = 1