I'm trying to write a web application that would use Twitter via OAuth.
I run my local server as 'localhost', so I need the callback URL to be something like http://localhost/something/twitter.do but Twitter doesn't like that: Not a valid URL format
I'm probably going to do a lot of tests, but once I've approved my app with my username, I can't test again can I? Am I supposed to create multiple twitter accounts? Or can you remove an app and do it again?
In answer to (1), see this thread, in particular episod's replies: https://dev.twitter.com/discussions/5749
It doesn't matter what callback URL you put in your app's management page on dev.twitter.com (as long as you don't use localhost). You provide the 'real' callback URL as part of your request for an OAuth token.