The man who came up with the default test for intelligence didn't come up with a test for emotional responses. In "Blade Runner" the test for "replicants" is based on physiological responses for emotion.
The biggest problem is that it is clear that "replicants" do in fact have emotions based on the very premise of the movie. And knowing what we know about the range of emotions in "normal" people, it is clear that looking for "abnormal" is a lot trickier than thirty to forty questions about turtles on their backs or a child's butterfly collection.
Now there are "universal responses" in humans. Anger, fear, and unease all have certain physiological signs. However these are hardly a way to test for humanity, given that those base responses truly are universal. If somehow the replicants were not genetically engineered beings (and the conversation between Roy and Tyrell makes it clear that they are) then approach taken by Blade Runners to identify replicants would be valid.
Unfortunately that is not the case. On the flip side, it makes for more interesting viewing than seeing Decker take a blood sample to identify by genetics. Much more dialogue with the flawed test.
The real question is where we draw the line about humanity. As the character Rachel showed, with an emotional framework even a replicant could provide the "correct" responses to the emotional stimulus test. However, that damned genetic test makes the whole premise of a replicant passing as a human a moot point.
In a broader context "Blade Runner" and "Millenium Man" are almost the same movie. What truly makes us human, and what truly makes humanity worthy to lord over it's own creations. If you liked "Blade Runner", consider watching "Appleseed" to see the flip side of the premise, what happens when the synthetic beings are in charge?