iPhones have a long lifespan. And this means that there's a very healthy second-hand market. But How do you know if that iPhone is good?
Quite a few readers have asked me whether iPhone's have some sort of built-in diagnostics mode that can be used test the health of the components. Apple has such a tool, but it's not part of the iPhone, so we have to rely on the third-party app market.
I've been playing with a number of different tools over the years, and the best one that I've come across is to do this is TestM.
It's not perfect, but it's pretty good. It's also free, which is a good start.
Before I go any further, I want to point out something. The TestM app also offers insurance, trade-in, and find a repair shop features. I have not tested any of these and have limited my focus to the diagnostics feature. Note also, that contrary to what some reviews state, this app no longer displays ads.
OK, with that out of the way, the diagnostic mode offers 26 tests, which range from testing the cameras, touchscreen, microphone, and even the haptic engine, to a comprehensive stress test that pushes the battery and thermal dissipation to the limits.
A full test can take around 20 minutes in my experience, and it does take a certain amount of user interaction (you're asked to move to each test, and some tests involve you listening to the speaker or the haptic engine and giving feedback. Bear this in mind, as these tests aren't something you can just hit begin on and walk away.
You're involved in this!
It's a good app. Not perfect, but it does have to operate within what Apple allows apps to do. For the price -- zero dollars -- it offers quite a deep dive into the health of your iPhone and its components.