Did you know that you can run executable programs with F9 instead of F8 in recent versions of ADT (SAP NetWeaver Application Server ABAP 7.52)?
Running a program with F9 redirects WRITE outputs to an “ABAP Console” in ADT. No SAP GUI is needed any more.
But hello? Who who on earth is still willing to use WRITE?
Good to know, that CL_DEMO_OUTPUT also writes to the ABAP Console after F9!
You can also reach the console by implementing a special interface in your classes (from ABAP 7.51 on). But for small pieces of executable test code CL_DEMO_OUTPUT might be an option.