Customize the values at the top and then run it with
$ ./tclwebtest install.test
There is some stuff in it to save an existing parameters/nsd.tcl file, delete that if you don't need it.
There is one major drawback - tclwebtest is not able to access webservers on other ports then the standard web port 80. This is due to a bug in the tcl http package (already reported) I believe. So you need to run this with root privileges if you want to start your webserver to run on port 80. (And of course an installation script must be able to restart the webserver). Or you have some virtual hosting set up.
No guarantee that it works on any other machine then mine though - I would like it to be more general but it definitely needs more work.