Hi there,
there are some testing tools like this one that generates the display using a real device:
https://www.browserstack.com/responsive
Unfortunately they are premium tools.
Personally i find the repsonsive views in the browser developer tools to be pretty darn accurate.
And if you’re using a Mac you can fire up Simulator which is part of their XCode plugin and run real world sims of iPads and iPhones – and that is 100% accurate.