Battery, alternator and starter all tested good at mechanic. but!

Battery, alternator and starter all tested good at mechanic.
The car still didn't start this morning wondering if it could
still be the battery even though it tested good maybe it was
charged from driving around for a while. Or if it could be
something else when I try to start I get a series of clicks
with lights and display screen coming on with no struggle.
Then starts instantly with a jump. also starts fine rest of the
day so far after driving it around on and off. Second
morning this has happened.