message: Ensure that the root Id is in the list
  Summary: The invariant is that all mentioned id's must show up, so make sure we do that. Can be triggered by the test in 2 diffs time.
diff: @@ -202,6 +202,7 @@ impl Heap {
  last_changed: start,
  call_stack: vec![(root, Duration::default(), start)],
  };
  + info.ensure(root);
  self.for_each(|x| info.process(x));
  // Just has root left on it
  assert!(info.call_stack.len() == 1);
  