I'll test you on your knowledge of traffic lights

driving school

D.I=Driving Instructor

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D.I: The rules of the road. You must obey the rules of
the road at all times. That means obeying the traffic signs.
Man: These are all traffic signs?
D.I: Yes.
Man: Oh, What are these lights?
D.I: Traffic lights. I know. I'll test you on your knowledge
of traffic lights. What do you do when the lights is red?
Man: I don't know.
D.I: You stop. You bring your vehicle to a complete stop.
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What does "on" mean in this sentence?

Does it mean"about" or something else?

I'll test you about your knowledge of traffic lights.

Thank you