Instead of copy-paste same docstring, maybe just move the whole section from the main docstring here.  For example:

   *  subtest-command:the invalid charactor occurs in [COMMAND]
       *  the command parameter is invalid.(e.g. -@, -^) 
       *  the command parameter is availble, but the behind value is invalid.

This way, the documentation for the sub-subtest is right next to it's implementation. That makes it **much** easier to keep updated if/when the code changes.

BTW: The reason I'm so careful about test docstrings is, someday we will automatically include them into the main documentation (similar to how we do for the API docs).  This way there will be no separate updating of ``index.rst``.  So the "Cleaner" the docstrings are, the prettier they main docs will be :grinning: