(Credit: Lance Whitney)

You're running into a problem with your iPhone or Android phone. Perhaps you just bought the phone used or refurbished and are concerned about technical issues. Or maybe you want to sell your phone and need to track down any potential problems first. Either way, you can check out your phone with a series of diagnostic tests courtesy of an app called TestM.

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Available for iOS and Android, the free TestM app can run a variety of tests on your phone. You can choose a quick test to check three key features -- your touchscreen, your earpiece audio, and the high-frequently audio. You can opt for a full test, which examines all the accessible features. You can run tests on a specific category, such as Screen or Hardware. And you can test just one specific feature. After the test completes, the app can generate a report to show you the results. You can then share the report via email, messaging or another app or service.

Uncovering the source of technical trouble on your mobile phone isn't an easy task. Apple has its own diagnostics tool for the iPhone, but that requires either a visit to your local Apple Store or a phone call to Apple to run a remote diagnostic session. The App Store hosts only a few select diagnostic apps, such as Phone Diagnostics and 8x8 Diagnostic Tool. And what about Android? On certain Android phones, such as those from Samsung, you can access an internal diagnostic tool. (Open the phone dialer and enter *#0*# using the dial pad.) Google Play does house a variety of third-party diagnostic apps. But whether you have an iPhone or Android phone, you can cut to the chase with the TestM app.

To run TestM on your phone, select the full test, the quick test, or a specific category or feature. Each test is interactive. The touchscreen test requires you to draw on the screen. The microphone test asks you to speak. The audio test prompts you to tap whatever numbers you heard. And the camera test requests that you pose for a picture. If you opt for the full test, you can skip any features you don't want to test. A few tests are specific to the phone. For example, the iPhone tests can check for issues with Face ID or Touch ID. But most of the tests are generic and work the same across both iOS and Android.

Of course, since TestM is a free app, there is one drawback. Yes, ads. As you run the tests, especially the full range, expect to get interrupted by an occasional ad. In some cases, you can quickly close the ad; in other cases, you have to wait a certain number of seconds to dispense with it. But as always, the developer has to find some way to support a free app.

After the tests complete, you can ask the app to create a report. This report displays the vital stats of your phone, such as processor, memory, screen size, resolution and OS version. From there, you can check out the results of each test. TestM gives each series of results a health grade or percentage. Each individual feature tested gets a green checkmark for good or a red checkmark indicating a problem. For problematic features, you can tap the result to run the test again.

Finally, you can share the test results with another person. The app even gives you an option to send a report to a buyer if you're looking to sell your phone. And if the phone is in need of repair, TestM will even display a list of local repair shops.

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  1. The TestM app can run a variety of diagnostics tests on your iPhone or Android phone and deliver a report of the results.
  2. The app can check out your touchscreen, audio, microphone, camera, and a host of other features.

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Lance Whitney is a freelance technology writer and trainer and a former IT professional. He's written for Time, CNET, PCMag, and several other publications. He's the author of two tech books - "Windows 8 Five Minutes at a Time" and "Teach Yourself VISUALLY LinkedIn."