test

   'test' ['d'|'v'|'n'|'e'|'p'|'l'|'c'|'s'|'b'|->
           'S'|'L'|'se'|'sh' <entity-name>]
          ['i' <set1> <set2>]
          ['o' <set>|<node>]

A boolean opperation. Usually tests the existence of a given entity (watch the '\' which prevents the value beeing replaced by its content!):

test v \value

And it checks if at least one node included in set1 is inside the elements included in set2:

test i nodeset elemset

Or it tests the observability 'o' of a certain node under the given orientation of the model. The node can be given as a member of a set or directly by its node-nr. The command returns TRUE or FALSE and writes it to the ”stack”.