Actually, no. You don't need to create a war archive to test a servlet....
You do need to create an directory structure that "looks like" a war archive, and then you can use directory deployment to "upload" your servlet to the web container.
Take a look at asadmin's deploydir subcommand.
Note: if you use deploydir and you are doing jsp development, you can shorten your developmment cycle to: edit jsp, save jsp, reload jsp page in browser...
You may want to read through
http://blogs.sun.com/vkraemer/entry/a_history_lesson_of_deployment for even more information about deployment to servers built from the GlassFish codebase.
vbk
[Message sent by forum member 'vbkraemer' (vbkraemer)]
http://forums.java.net/jive/thread.jspa?messageID=213553