Checks the flash memory connected to an Espressif microcontroller (ESP8266, ESP32, ...), like memtest would check RAM on a PC, just less sophisticated.
Ensure your (virtual) environment has esptool.
esp_flash_tester.py [serial port] [flash size in MB] (baudrate)
Specify serial port like COM42 on windows or /dev/ttyUSB42 on linux.