Sparkle,
I do not wish to divert the thread here, but before you "doubt" what your engineers do on a daily check maybe you should enquire as to what is actually covered on a daily in your company. You might find that we engineers are allowed to get involved in the "nitty gritty" stuff you speak of and are usually very adept at rectifying any defects found on a pre flight.
In my present company a TCAS test is covered although an ADC BITE is not. However in a previous company the ADC's were tested and certified in the daily check. Requirements will vary between outfits, as a combination of aircraft maintenance schedule and company policy.