Testing an RCD switch by short circuiting neutral and ground
I've seen references which claim it's a valid test to connect the
  Ground and Neutral to test if the RCD switch will break.


That is only reliable if the potential difference between neutral and earth is sufficient to drive circa 30 mA through the RCD when neutral and earth are connected. However, it is a fail safe technique to some extent.


  Are there other simple ways to test if RCD works for a particular
  socket?


What's wrong with using the test switch on an RCD: -



All (?) RCDs appear to use test switches: -



Google results of "RCD test switch circuit" appears to show all RCDs with test switches and, where there are schematics, they all seem to use a resistor from live to earth to create the earth imbalance current.

Including wall sockets: -




  Would like to hear if it's possible to defend or disprove this
  approach on both a theoretical and practical level?


I can neither defend or disprove this approach because if it does work then it's likely the RCD is OK but, you haven't proven that in the right way.