All the programming, processing, testing, and editing (ARE or IS) done by James.
I would use "is". It sounds correct, and there is support from grammar too. While there are several parts to the job, there is no real sense of plurality. So with a subject containing "All the" and with no clear sense of plurality, I would use "is".
All (of) the programming, testing,..........is done by James.
Even with plurality, "is" is often correct.
All the wind and rain is a big problem.
I would use "is". It sounds correct, and there is support from grammar too.
It depends on whether we view them as united or separate, and there also may be differences between the variants. I see nothing wrong at all with the singular, but the plural sounds easier on my BrE ear.