Testing printed circuit boards manually can be a time consuming process. The almight algorithm recommended a video1 that describes how to make a “bed of nails” tester for PCBs. The “bed-of-nails” consists of a circuit board with pogo-pins at each contact point for the candidate PCB to be tested. The candidate PCB will be loaded with firmware that listens for input on each GPIO pin, I2C/SPI/Serial port etc. and sends back a pre-determined response. The tester is a simple microcontroller that listens for a serial command, sends a probing signal via the pogo-pins and transmits the response back over serial. The whole system is controlled by a script running on a computer (Raspberry pi?) that programs the target board with the test firmware, sends the commands to the tester and verifies the responses.
The production test procedure would involve pressing down the test article and clamping it down somehow on the pogo pins, and running the test script which returns a PASS/FAIL response.