Everything should be tested. Well everythings that is more than playing around.
Tests make your code better, more reliable and help find bugs. Though tests do add a massive overhead to changing your code.
And quite honestly I have probably spend more time writing tests then code that they test.
But in the end it was always worth it because they find bugs and tell me what I can rely on to work.
I like the "KISS" princliple, not just because of its name, so let us keep it simple stupid
(and yes I just researched wether or not to put a comma there).
A lot of testing Frameworks out there introduce a lot of overhead and semantics to your code.