my $tmp = fresh_workspace;
my $con = open_empty_con($i3);
-is(@{get_ws_content($tmp)}, 1, 'one container');
-is(@{get_ws_content($old)}, 1, 'one container on old ws');
+is_num_children($tmp, 1, 'one container');
+is_num_children($old, 1, 'one container on old ws');
cmd 'move workspace prev; workspace prev';
-is(@{get_ws_content($old)}, 2, 'container moved away');
+is_num_children($old, 2, 'container moved away');
done_testing;