Don has made a very good statement. The SOP of a circuit, or high voltage line clearance, is to test "live", and then test when "dead". The live test, tests the tester, also retest tester after clearance.
I once, had the blades of a disconnect, separate from the operating shaft. I pulled the handle and locked it with a padlock. The circuit was still live. There is occurrences of one, or more, blades not being disengaged. The test procedure should follow accepted methods.
