want to test all 3 mains.Whats your actual requirement?
If you simply want to test all mains 3 pin plugs for grounding then even a basic spike guard does the job.
The bulb and wire thing is the most cost-effective vfm and a basic thing every electrician depends on..
Check this-
I'm pretty sure the plug won't fit into the socket that way without a lot of force.Just use something like allout, mobile charger or something with 2 pin and plug it sideways. One prong in earthing hole and the other into a live hole.
View attachment 165351
If it works the your earthing is good.