Typically engines built are repeatedly hot fired to analyses their performance.
In between tests, what are the review that the engine undergoes? How is an engine gauged suitable for a hot fire static test?
There are a couple of things that wear out in rocket engines. What exactly wears out first depends on the design of the rocket engine. Some design choices put more load on a particular component, which increases the likelyhood of a compnent failure.
Therefore it's imortant to be familliar with typical problems with a specific design when deciding if the engine can be fired up again.
The three turbopump related things can be checked with a boroscope.