Due to the nature of my work I am someone that changes my phone a lot with my current phone being the superb Huawei Mate 20 Pro. I normally keep a few devices to hand, but phones that have gone unused for a while will be sold or given away.

When it comes down to selling or buying a used phone, you want to make sure everything is working perfectly, and this is where an app such as TestM comes in handy. I wouldn’t say this app is particularly revolutionary in what it does, but it helps buyers and sellers diagnose issues with phones that can sometimes go unnoticed. For example, in the past, I have had a couple of phones that have had issues with their GPS, but when you buy a phone used, this is probably not on your list of things to check, it could be well past the return period before you notice the problem.

TestM is simply designed with user-friendly instructions making it usable for people with no tech skills whatsoever. It is a free app to use with no limits on its functionality; however, there are quite a lot of adverts. If you are only using this once to test one phone, I would stick with the free options. However, if you regularly sell or buy phones, I would suggest it is worth paying the £4.59 to remove all the advertising. It is available on both Google Play Store and the Apple App Store

Once you have installed the app, you can run tests on individual features of the phone, or alternatively, do a quick test or full test. These two options provide a comprehensive test of your phone identifying all the aspects that could go wrong with a phone. I did the quick test at first, then completed the other elements through the full test. For the sake of an extra couple of minutes, you might as well just run the full test from the start so don’t miss any potential issues.

Some of the tests require more work than others, for example, the screen test makes you swipe your finger all over the screen removing the highlighted areas, this will make sure there are no dead parts to the screen. Similarly, the speaker and earphone options require you to listen to three numbers and type them back in. Other tests such as Wi-Fi, Bluetooth and cellular require no input at all (assuming they are enabled on your phone).

On top of the normal tests for the report, you can run a battery test which allows you to see if the battery has any issues with it. This is very useful as batteries will start to decay over time.

Once you have completed all the tests you can create a report which you can share to a buyer to give them peace of mind about the phone. Or if you are a buyer, you can use it as evidence that there is something wrong with the phone, rather than having to go through the painful situation where a seller makes you check various things in an attempt to get out of a return.

Furthermore, as a seller, you can save a photo of the report and use this as part of the listing for eBay or whatever service you are using to sell the phone.

If there is a problem with the phone the app includes a geotargeting tool to find local repair shops, this will obviously require the shop owner to sign up to the service, but in my relatively small town, I was able to find one shop listing locally.

Overall, I think this is a superb app that is well worth using as both a seller or buyer. It will make selling your phone much easier and avoid the inevitable stupid questions you can get from some buyers. Similarly, as a buyer, it gives you proof of any issues with a phone should you need to return it or make some form of claim to companies like eBay and PayPal.