I test machines every day. It doesn't seem to be that difficult to me.

The point was that this problem is framed badly. Humans won't be testing a super intelligent machine's morality. There's the man-machine symbiosis to consider.

Aren't rockets machines?

Testing machines may not be "easy" - but it isn't rocket science. You put the testee in a virtual world and test them there.

What if the testee realizes they are being tested and behaves differently than they would if unboxed?

Then, if you identify that as being a problem. you redesign your test harness.

Security by obscurity doesn't work well even against humans, so it seems best to use schemes that work even if the testee knows everything about them.

Furthermore, do you think a group of monkeys could design a cage that would keep you trapped?

Probably not - but that isn't a terribly good analogy to any problem we are likely to face.

An escaped criminal on the run doesn't have much of chance of overtaking the whole of the rest of society and its technology.

Are there any historical cases of superintelligent escaped criminals?

Well, of course not - though I do seem to recall a tale of one General Zod.

You sound awfully confident about a scenario that has no historical precedent.

I'm doubting whether the situation with no historical precedent will ever come to pass. We have had escaped criminals in societies of their peers. In the future, we may still have some escaped criminals in societies of their peers - though hopefully a lot fewer.

What I don't think we are likely to have is an escaped superintelligent criminal in an unadvanced society. Instead, I expect that a society able to produce such an agent will already be quite advanced - and that society as a whole will be able to advance faster than any escaped criminals will be able to manage - due to having more resources, manpower, etc.