My mathematical logic is rusty, but if I recall correctly, Gödel's incompleteness theorem basically states that it is impossible to solve this kind of question. No matter how many tests you run, there will always be an uncertainty.
An incredibly stupid example is that the rule could be "yes for strictly increasing, OR if one of the numbers is -18273192783127897981." You'll never know.
I understand this is contrived, especially when the test subject doesn't know. But if you do realize this while doing it, it makes the test a little frustrating..
EDIT: I see people are making a connection with unit testing, and the irony is poetic. This is precisely the problem Dijkstra was talking about when he said that "Testing shows the presence, not the absence of bugs."
An incredibly stupid example is that the rule could be "yes for strictly increasing, OR if one of the numbers is -18273192783127897981." You'll never know.
I understand this is contrived, especially when the test subject doesn't know. But if you do realize this while doing it, it makes the test a little frustrating..
EDIT: I see people are making a connection with unit testing, and the irony is poetic. This is precisely the problem Dijkstra was talking about when he said that "Testing shows the presence, not the absence of bugs."