drug testing questions

Apologies if this isn't the right place to ask, but I recently had my F2F interview with United and Im curious about the drug testing there. i am confident i will pass my first drug test to potentially continue into training if i get the job offer. If i am lucky enough to get a job offer, how soon do they drug test again? how often are drug tests done before/ during/ after training, and how often are random drug tests? Im confident in myself to say ill be quitting weed for good, and this potential job will be a big motivation for that. but if i get passed this first test and wish to celebrate a new job, i really dont want to throw my chances if there a 2nd test soon after