How to debug htaccess rewrite script

Question

I was wondering how to create and debug this kind of script that can become a bit of headache if you are not used to write them (like me).

Do you use tool to create

Answer 1

Note to readers: the old answer doesn't work anymore.

As of version 2.4, Apache no longer allows the RewriteLogLevel and RewriteLog directives. Now they're all bundled with the single LogLevel directive (see Log Files documentation), which supports module-specific log levels with prefixes and trace[1-8] constants. To set the highest level of logging specifically for the rewrite module, you now use the following:

LogLevel warn rewrite:trace8