+Adding and testing your lexer
+To make pygments aware of your new lexer, you have to perform the following
+First, change to the current directory containing the pygments source code:
+Next, make sure the lexer is known from outside of the module. All modules in
+the ``pygments.lexers`` specify ``__all__``. For example, ``other.py``sets:
+ __all__ = ['BrainfuckLexer', 'BefungeLexer', ...]
+Simply add the name of you lexer class to this list.
+Now update the ``python.lexers._mapping``. This is a generated module which
+can update itself changing the current directory to its location and simply
+Without the ``cd`` command, you will get an ``ImportError``:
+ ImportError: No module named ez_setup
+To test the new lexer, store an example file with the proper extension in
+``tests/examplefiles``. For example, to test your ``DiffLexer``, add a
+``tests/examplefiles/example.diff`` containing a sample diff output.
+Now you can use pygmentize to render your example to HTML:
+ $ ./pygmentize -O full -f html -o /tmp/example.html tests/examplefiles/example.diff
+Note that we explicitely call the ``pygmentize`` in the current directory by
+preceding it with ``./``. This ensures your modifications are used.
+Otherwise a possibly already installed, unmodified version without your new
+lexer would have been called from the system search path (``$PATH``).
+To view the result, open ``/tmp/example.html`` in your browser.
+Once the example renders as expected, you should run the complete test suite: