In order to provide developers with a reasonable way to test their alert-handling code, starting next Thursday, automated weekly alerts will be made on testnet.
They will contain the message "[TEST] This is a test alert broadcast at $TIMESTAMP" (where $TIMESTAMP is the unix timestamp of initial broadcast), will expire in between 2 and 4 hours and will have varying prioriry. They will be announced at 13:00 UTC (currently 9am EST).