Random checks are rare, in 20+ years on the line, I’ve only had 2 both in Scandinavia, even though you know you are sober it’s still a little stressful for the whole crew.
Personally I would not get on an aircraft if I suspected a member of the crew were intoxicated, the problem is that unless they reek of alcohol or are clearly drunk in terms of their behaviour it’s not an easy call.
Hopefully I’m never put in that situation, but I suspect we are only seeing the tip of the ice berg here