The entire idea of the Turing Test is that once a machine is created that is indistinguishable from a human being (at least through a text-based interface), an observer would have no rational basis for denying that machine the status "intelligent being". All other reasons (e.g. religious doctrine, "common sense", et al.) would necessarily be irrational.

This is owing to the fact that, in the absence of an irrational presupposition, our only means with which to judge a being's 'intelligence' or 'consciousness' is by comparing what we can perceive through our senses with examples from past experience. This is because 'consciousness' and 'intelligence' are not externally observable qualities like, say, 'redness' or 'relative speed'. They can only be percieved through the secondary traits we associate with them, like 'sense of humor'.

Note that this is true regardless of your views on mind/body dualism and subjective vs. objective reality. It does presume that you believe 'consciousness' to be an extant state; if you do not believe this, however, the entire matter is irrelevant, as you do not believe humans are intelligent either. You're also probably either a sociopath or a hardcore nihilist.

The fact that a human built the machine and understands every detail of how it works is of no importance. It is quite possible that consciousness is an emergent trait rather than an intrinsic one; it may simply be the result of a particular sort of complexity. This would mean that understanding every detail about a creature's construction would not necessarily equate to having a complete understanding of that creature. Also, consider this: a being could concievably exist that understands every detail of human behavior, both how and why people are as they are. This being could also have created us. The existence of such a being would certainly not negate human intelligence; indeed, there is no reason this creature couldn't be a human.

Look for this node to become relevant in your day-to-day life about twenty-five years from now.