What is the system test feature on the Honeywell FocusPro TH5220D?

To initiate a system test, press and hold the 's' and 't' buttons until the display changes. Use the menu to perform several tests including heating system (test numbers 10-13), cooling system (tests 30/31), fan system (40) functionality checks. Follow prompts to turn on/off various systems components one at a time as indicated in respective test conditions listed on page 8.