Updated: Jan 2, 2019
The digital landscape has been dominated by USB, or Universal Serial Bus, since the late 90's.
It's important to properly, and easily, troubleshoot USB devices because our technological lives revolve around them. USB devices do one, or both, of two things: Transfer electricity, and transfer data. There are three main factors in any charging/data transfer; the charger or power source, the cable, and the receiving device. It does however become more complicated when you dive into USB controllers, which communicate before any power or data is transferred to determine the proper amount of current and data rate. Enter the USB tester, allowing me to easily locate problems in the entire process.
This device wirelessly communicates with my phone or computer to provide additional data and features. I can even determine the health and full capacity of a USB battery pack, or view the resistance your aftermarket charger cable provides vs. the OEM (factory) one that was included with your phone, so you know which to use most of the time for faster charging. Consider that data transfers cannot complete properly with too much resistance, nor will "fast chargers" function if the data lines aren't connecting. They'll still work, but they won't be able to communicate with your phone the highest amperage to send. If your technician does not have a USB tester they should know how to test them manually with a multimeter and oscilloscope. Our computer world is dominated with this technology and it's essential to troubleshoot it efficiently.