Felipe

You have a local installation (eg. <code>localhost/blogs</code>) and use it to develop and test all your themes. With this plugin activated, every time you switch themes the blogname option will be updated to match that theme name.

Site Renamer

Update the site name to match your current theme name. Useful for local development!

jorgecasar

If you have the capacity of “edit_themes” you can see a Try Theme, a new option in Design menu.
In this page you see a form that let you choose a theme and it will be activated while you’re login in.

Try theme to develop

This plugin detect if current user have the capacity of "edit_themes" and then he can change the template to develop it.

Site Renamer vs Try theme to develop