..No point in testing a fuse it's not an electromechanical device, MCB's can be tested both for short circuit as well as overload you cant however measure the disconnection time, but as long as your Zs meets the limits you have satisfied the requirements of 7671, my point was and for some reason M seems to want a handbag fight over it that what gets plugged into an E/Lead is an unknown quantity and I refuse to leave a lead on site that has the capability to have a larger fuse fitted than the CSA of the flex can support, in much the same way as I wouldn't walk off an install and leave a 32A CB in a single 2.5 T&E radial I get it but then again I suppose if you happen to have an odd broken drill bit or nail they might wedge that across the board