result = vm.execute( "+", "7, 8", null );
assertNull( result.getError() );
assertTrue( result.getStack().size() == 1 );
assertTrue( result.getStack().peek() == 15 );
result = vm.execute( "-", "7, 8", null );
assertNull( result.getError() );
assertTrue( result.getStack().size() == 1 );
assertTrue( result.getStack().peek() == -1 );
result = vm.execute( "*", "7, 8", null );