"Test & Check for iPhone" is a utility tool designed for diagnostics and hardware monitoring on Apple devices. It is often bundled with or categorized under "My Device Info" apps on the App Store .
Dial *3001#12345#* followed by the call button to reveal advanced network settings and cellular data information, as explained in this Wilson Amplifiers blog post . Test & Check for iPhone
You can initiate a hardware test by turning off your phone, holding both volume buttons, and plugging it into a charger, according to this YouTube video . "Test & Check for iPhone" is a utility