no sorry i meant i'd check to see if the £2 tester was still working, so for example i'm changing a light in the kitchen, lighting circuit is off, i check for voltage using the £2 tester, if it doesn't light up then i'd check it on a known source i.e the kitchen ring or the DB and if it lit up then i'd crack on, but if it didn't then i'd have to go and get something else to test it with(voltage/continuity tester leads) as the £2 tester has obviously developed a fault! never had one go faulty yet though i've used fluke and metrel ones for the past few years, it's such simple technology if used right i can't see there being a problem with the cheap one either.