Are you a professional programmer?

[marcel]

You'd be surprised to find out that they all are developing software, but of course, not by your definition, which is like 50 years old.

They are part of the software development process(which consists of all those phases, not necessarily in that order), therefore they are developing software, even if some of them do not write actual code.

If he tests software to find out what and how to (of course, he thinks about code) improve a feature, than yes.

A tester usually looks for bugs, not new functionalities or improvements.