The plastic pieces hold down the PCB against the pogo bed. This tester, when used with a little batch script, performs the following test:
- Reprograms the board's fuses and flash with a bootloader (via the ISP port). For this part we're using the Arduino as an ISP programmer (there's a sketch that does this)
- The computer then bootloads (via USB) a pin-by-pin testing program
- Once the board indicates the test completed, the computer erases the testing program