They have been using these 'tests' here in the states for a long time.....it involves when an officer holds a pencil in his hand and asks you to track it with your eyes, without moving your head. Your eyes, the theory goes, will not smoothly track the pencil, if you are high.
I don't know how much validity there is to these tests, but that is a moot point.
Why is it moot, spice, you may ask???
(Constitutional Law 101)
Because these test are a SEARCH, and according to the LAW, he must have PROBABLE CAUSE for said search.
Tell his ignorant ass NO when he holds that pencil up.
People are so conditioned into having conversations with these bastards that, in the course of the conversation, he ambushes you by holding a pencil up, 999 people out of a thousand meekly comply.
Let me tell you something, if they pull me over, I crack the window about an inch, hand over my license and registration/insurance, and roll the window back up.
You DON'T have to engage him in conversation.
It's none of his business where you're going.
Make him do his job, don't bend over.