Well no; those probabilities don't add (otherwise after 4 rounds you'd be at 100%, clearly wrong.)
At 1/4 per round, the chance of getting tested exactly once out of 3 rounds is 1/4 x 3/4 x 3/4 x 3 = 42%
I.e., 25% of getting tested in any 1 round, but not the other 2.
Or, from the other...