This predicate succeeds if all the tests succeed and fails otherwise (i.e. it is "semi-deterministic")

Below, the printout has been removed, which can be more or less achieved with

set_test_options([silent(true)])

Example:

:- begin_tests(fail).
   test("just fail") :- fail.
:- end_tests(fail).

Then (removing the printout):

?- run_tests.
false.

Another example:

:- begin_tests(succeed).
   test("just succeed") :- true.
:- end_tests(succeed).

Then (removing the printout):

?- run_tests.
true.

Yet another example:

:- begin_tests(partially_succeed).
   test("just succeed") :- true.
   test("just fail")    :- fail.
:- end_tests(partially_succeed).

Then (removing the printout):

?- run_tests.
false.