ng block
  (if that is definite) or an infinite size (when it is indefinite).
  https://drafts.csswg.org/css-sizing-4/#available

  - - - - - - - - - - - - -

  Inside this batch of 24 sizing-orthog-vlr-in-htb tests:
  001-012: body has 100px margin-top and 100px margin-bottom
  013-024: body has no vertical margins

  Inside each sub-batch of 12 tests:
  001-006: containing block's height is 'auto' therefore indefinite
  007-012: containing block's height is 400px therefore definite

  Inside each sub-sub-