What is the best way to write cross-platform applications?

Question

Cross-platform

Suppose I am writing an application that should work on both Windows and Linux. How smart is testing it in Linux (or vice versa). VM rises on it Linux is put. The assembly starts on Windows, then on Linux and the result looks or what?

Answer 1

Developed on any convenient OS. When everything is ready, we put the virtual machine, test it there, fix all the jambs that got out, check again in the first OS, and make a release)