Does Aon background check mean drug test?

I have the final interview coming up for an accounting/consulting position at a mid size subsidiary of Aon. In my first interview it was indicated to me that there would be a background check but it didn’t occur to me until now that it could mean a drug test is included. I have only smoked occasionally in recent weeks and If i stop now I may be able to pass in a few weeks but I was wondering if anyone had any experience in this regard? Would they have told me explicitly there would be a drug test? How long (estimably) would I have to take a potential test upon being offered a position?

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