How do I test to see if modpython is functioning correctly?

First, you must edit or create
a .htaccess file. Inside the file, insert:

AddHandler python-program .py
PythonHandler mptest
PythonDebug On

This will tell Apache how to handle a specific file. modpython,
by default, does implicitly perform any function, unless explicitly defined
by a directive (each line in the '.htaccess' file).

Next, create a file, in this case because 'PythonHandler' is set to mptest
and 'AddHandler' is of the extension .py, the file that Apache will process
as a Python script will be named mptest.py. Insert:

from mod_python import apache
def handler(req):
req.send_http_header()
req.write("Hello World!")
return apache.OK

Notice also, that indenting is very important with Python as no explicit usage of braces to enclose control structures is used.