The testing looks at your interests and ways of looking at work, and match it up to see what group of workers you most resemble. For example, teachers tend to be very conservative in many ways, as they do the same thing year after year, and the culture has usually been pretty static.
There are also aptitude tests, to learn your relative strengths and weaknesses.
But this comment:
— “I know that jobs are not for fun …” —
Nope. Work can be the most fun part of your life.
You seem to be somewhat aware of yourself. Why not try starting up some kind of little business? could be service, or something else.
Be an entrepreneur.