Car won't start (sometimes)

Sometimes in the morning I go out to start my car, the radio and all the sounds come on, the lights come on, I turn the car over and I hear one click. I took it for diagnostic testing and all the amperage checks out for the starter and the battery. However, they think it is the starter motor on its way out. Any thoughts?

Facts please, JT

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Did they do anything other than test? Did they clean battery terminals or wire connections or anything?