Injectors -- dirty or shot?

are there symptoms or tests that would tell you if injectors need replacement or just cleaning?
mechanic is giving us verdict tomorrow, but we think he went too quickly to the extreme prediction…
car runs like it’s missing, makes a warning beep when the rpms get a little high. a renault with an electronic ignition kinda like the prius has nowadays, but this car is about 10-12 years old…

Can you be clear about your make/model/year?

And what are the observable symptoms that led you to bring the car in?

The car is “about 10-12 years old”? I take it you’re not the original owner? And how many miles does this car have on it?

Offhand, if you have an injector malfunctioning I think he’s doing the perfectly responsible thing in changing it. That’s what most shops would do. That’s what I’d do.

Let me ask you, how long should a mechanic have to spend for the diagnosis to be believable? An hour? Two hours?

And, please realize that I’m trying to put things into perspective here and not to be sarcastic, if you consider a new injector an “extreme” repair, how would you categorize a bad main bearing? Earth shattering?

Honestly, I see nohting in your post that causes me to be suspicious of the mechanic or of his diagnosis or approach.