> we are actually trying to define intelligence through IQ tests, for example

Fail. IQ tests only measure how well you do on IQ tests.

> The problem here is that not every human being is intelligent

Unless they're in a vegetative state, they are more intelligent than any artificial system, so far.

> Is that the way you formulate tasks for software engineers?

The only way to make a specification so precise that it does exactly what you want is to implement it, and then the code itself becomes the specification.