RosettaCodeData/Task/Assertions/Liberty-BASIC/assertions.basic

a=42
call assert a=42
print "passed"

a=41
call assert a=42
print "failed (we never get here)"
end

sub assert cond
    if cond=0 then 'simulate error, mentioning "AssertionFailed"
        AssertionFailed(-1)=0
    end if
end sub