Bluetooth device spurious emissions test
This test mode is initiated using a special AT command, just like the other AT commands sent to the module (I only have experience working using the AT command method of controlling a Bluetooth modem; I've never used the HCI -- Host Controller Interface -- layer, but I'm sure there is an equivalent method of entering this mode).

If I recall (it's been a couple of years since I've done this) the command lets you specify a channel frequency and power level (typically maximum level is used), and puts the transmitter into a state where it is continuously transmitting alternating 0's and 1's.  There is no connection made to another Bluetooth device.  This testing is typically done inside an anechoic chamber, so it doesn't interfere with anything.