anchor.diff:                "http://example.root/A"
                 "http://example.root/A2" "http://example.root/A1")))
   
  -(prove:subtest
  -    "Visiting other branches should not reorder the nodes."
  +(prove:subtest "Traverse all history."
  +  (prove:is (htree:all-contiguous-owned-nodes-data
  +             (htree:back (make-tree1)))
  +            '("http://example.root"
  +              "http://example.root/B"
  +              "http://example.root/B2" "http://example.root/B1"
  +              "http://example.root/A"
  +              "http://example.root/A2" "http://example.root/A1")))
  +
  +(prove:subtest "Visiting other branches should not reorder the nodes."
     (prove:is (htree:all-contiguous-owned-nodes-data
                (htree:go-to-child
                  "http://example.root/A2"
  
positive.code:     (htree:add-child "http://example.root/B2" tree)
      tree))
  
  ;; (defun make-tree2 ()
  ;;   (let ((tree (htree:make)))
  ;;     (htree:add-child "http://example.root" tree)
  ;;     (htree:add-child "http://example.root/A" tree)
  ;;     (htree:back tree)
  ;;     (htree:add-child "http://example.root/B" tree)
  ;;     tree))
  
  (prove:subtest "Single entry"
    (let ((history (htree:make))
  
negative.code:     ;; TODO: Go to other child.
      ))
  
  (prove:subtest "Simple branching tree tests."
    (prove:is (htree:value (htree:current-owner-node (make-tree1)))
              "http://example.root/B2"))
  
  (prove:subtest "History depth."
    (prove:is (htree:depth (make-tree1))
              2))
  
  (prove:subtest "History size."
    (prove:is (htree:size (make-tree1))
              7))
  
  (prove:subtest "All contiguous history nodes for current owner."
    (prove:is (htree:all-contiguous-owned-nodes-data (make-tree1))
              '("http://example.root"
                "http://example.root/B"
  