Following the Idle: mock Text class and test thereof created #18365
I am trying to improve the _decode function because most of the Idletests needs the mock text and requires some more features to handle indexes.
Started improving the mockText _decode method while writing unit test for AutoExpand.py at #18292. 
For now I want the mock text to decode following indexes: 
line.char, insert, end, +-#c/chars, lineend, linestart, wordstart, wordend

For this I am trying to write regular expressions to extract the parts of index.
The submitted decodeTest.py is a sample script to show how my regular expression starts manipulating the decoding of indexes.

I have attached a checklist of several indexes. So you can easily run them and get an understanding of my approach.