To screen for nicotine consumption (especially cigarettes), it is possible to use urine tests or saliva tests.
The difference lies largely in the ease of use. The saliva test is considered less invasive than the urine test. The saliva test does not require any special convenience (toilet) and is done in front of you. It is therefore virtually forgery-proof.
Technically, the saliva test is much more sensitive and complex to manufacture, because traces of cotinine are less abundant in the saliva than in the urine. The saliva test is therefore a little more expensive to purchase.