While I would agree with scotman with regards having any suspect wiring checked out – he is wrong to suggest that a plug-in tester is able to identify Earth & Neutral swapped.
In many domestic and industrial installations, Earth and Neutral have a common electrical connection. The reason ‘earth leakage’ or ‘ground fault’ interrupters work, is that they respond to an imbalance of current flowing between Live and Neutral.
Recently, I suffered an RCD operating whenever anything was plugged into a socket within newly wired trunking. A socket tester indicated nothing wrong with the socket outlet – however when removed, Earth and Neutral had been transposed.