That is Mobile Safari (not that, AFAIK, all iOS web browsers use the same rendering engine). There is no good way to test it in outside of using an iPhone (or other iOS device).
The nearest you can come is to use the XCode iOS simulator, but even that requires a Mac to run it.
You could consider using another version of Safari, but: There are no versions of Safari for Linux. The Windows version of Safari (which you could run under WINE) has been discontinued and is very out of date. The Mac version of Safari won't run under Linux. All of them have differences from Mobile Safari.
Using another browser resized to the right dimensions won't give you the Mobile Safari rendering engine.