According to the manual, FR255 is able to :
1) Conduct an FTP Test : www8.garmin.com/.../GUID-C8DAC4B1-3159-4E8C-ADD9-6FA012EBA697.html
2) Automatically detect FTP : www8.garmin.com/.../GUID-0EDC68E3-D886-48D2-B624-AA634739B421.html & www8.garmin.com/.../GUID-B40A5128-C382-4F10-AD38-39649C42EF35.html
But my watch :
1) does not have the "FTP Guided Test" in Cycling activity => Training (even though a power meter and a chest heart rate monitor are paired)
2) does not have an option to autodetect FTP in User Profile > Heart Rate & Power Zones > Auto Detection (it only has options for max heart rate and lactate threshold)
Thanks