Whenever you design for responsive and various screen sizes, you need to test them to make sure that every element of the website is working properly, interactions are right, the menu is not breaking etc.
Here I am trying to list few tools which will help you test any responsive design:
Web Based Tools:
Google Chrome Extensions:
Firefox’s own Web Developer Tool (File > Web Developer > Responsive Design View (CTRL+SHIFT+M))
Interesting Articles on Responsive Design
What are you using?
Why not you share with us what you are using to test responsive design ?