Safest Way To Test 'Old' Wiring To Make Sure It Is 'Old'

[kbaud2002]

Hi - I Had a rewire done last year and Im just refitting the Kitchen - behind the old cabinets i found a junction box with a 2.5mm cable coming in through from under the floor and another 2.5mm cable coming out thats been snipped - ie it doesnt go anywhere. Now I'm almost sure that when I had the re-wire and had new kitchen sockets fitted that this must be part of the old wiring left behind but I'd like to know how to safely test it before trimmimg it back to where it emerges from the floor.
Can I use one of those screwdriver testers safely on this and do I just need to touch the (what would be) live wire to test it.
I also had central heating fitted with the old hot water tank etc removed - there is still the immersion switch on the wall and I would like to test this safely before removal - the switch has a red light indicator on it which dosent light now when switched 'on' but again I'd just like to be doubly sure I'm doing everything safely before removing these, what I think, are 'old' fitments.
Many thanks in advance.

 

[breezer]

best way is to invest in a multi meter and learn to use it and then open the jb and meter it.

regarding the immersion heater it may have had the fuse (in fcu, if fitted) removed, best check as above.

tester screwdivers give false radings and should not be relied upon

I am not being sarcastic (or similar) when i say get a meter, its just you asked for the best way. After all you wouln'd hit a nail with a shoe would you? right tool for right job

electricty has no prejudices, it kills any one