Shop says starter is good, but I think it needs replacement.

My Toyota Tundra v8 5.7 4x4 SR5 Double-cab has been starting weak lately, maybe the last three weeks like it is slowly catching or something.

Anyways the other day, it just wouldn’t start, and I got a shop to tow it and went and picked up the starter from Toyota. Well anyways they said that they were able to start it 15 times and the starter and battery were good, but it being at 137k miles, and maybe being an intermittent no start, I told them lets change it anyways.

Any advice?