In general:

• The tracker sends out low-energy Bluetooth announcements including its unique id
• a nearby iPhone hears those announcements
• the iPhone uses its current location
• the iPhone sends the tracker id and the location back to Apple via WiFi or cell
• Apple notifies the owner of the tracker where the tracker was seen

regress with old bugs

Have it write a test suite that enforces the correct behavior, and tell it that the test suite must pass after any change. Make sure it’s not cheating (return true) inside the test suite.