The test point on a Vivo Y91 (Mediatek chipset) is crucial for flashing the device's firmware when it's bricked or inaccessible through normal methods. It allows you to bypass the phone's bootloader and directly connect to the device's memory for flashing. Finding the correct test point is essential to avoid damaging the device. This involves carefully opening the phone and shorting specific points on the motherboard, as shown in the following images, while connecting it to a computer.