You need a multimeter, which has a voltmeter, ampmeter and ohmmeter. The ohmmeter will measure the resistance of a given conductor. If your resistance is near 0 ohm, then you are sure you have a continuity.
A multimeter isn't expensive here are some for home:
http://www.sears.com/shc/s/p_10153_12605_03482139000P
Put the multimeter in ohmmeter position. You connect one test lead to a ground outlet (the round socket of the three on any outlet) and you connect the other lead test to your earth ground (which is the incoming water pipe in most houses). Measure near 0 ohm for a continuity. If what you measure has a high ohm value, like 10Mohms, then you are sure your ground outlet isn't really grounded.
Hello Tez. I'm from Canada and in Direct Current application, black wire are usually linked to reference point or ground. BUT NOT IN AC. In AC, it's the green wire, the white wire being the common return of the AC, not linked to the ground. The black wire is the "
alive" wire, don't ground it at any cost before measuring it with a voltmeter first. Of course, there are different color coding then North American, but be really sure before, an electrician advice is always the best to do.
Namaste, Steven