The big caveat about testing, which the president didn't seem to understand when speaking about the VP's press secretary testing positive, is that you could be unknowingly infected on day 1, become contagious to others while asymptomatic on days 3 & 4 but test negative, then test positive on day 5 while possibly still feeling well. (Or not.) A test is a value in time which can change in 24 hours.
Bruce, nice to know someone else pays attention to the relevance of R0 and herd immunity levels. You're right about measles having a higher number than SARS-CoV-2.
