expect: "idx0idx1idx2idx3"
nodes:
- ts: 1
  content: "idx0"
  to: 0/
- ts: 0
  content: "idx1"
  from: 1/
  to: 2/
- ts: 2
  content: "idx2"
  from: 0/
  to: 3/
- ts: 3
  content: "idx3"
  from: 2/