There's no good test. Otherwise, that would be the interview process. Usually, it is just others' opinions of you. You might try a bunch of different jobs, be

There's no good test. Otherwise, that would be the interview process. Usually, it is just others' opinions of you. You might try a bunch of different jobs, be bad at them, but eventually find a great fit where everyone respects your work. Those prior opinions don't really matter now, do they? One of the other key problems why it's difficult to answer is that the standards of development change very rapidly. You'd likely find the same questions in the spirit of "what makes a good punch card developer?" when those systems were around. There were probably a lot of interviewers with a lot of heuristics to hire the best, but those specifics don't matter any more either. And sometimes, it comes down to simply marketing yourself well or having good salesmanship or playing office politics.