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fips/testing/chaos/sim
Johnathan Corgan e9ca741e53 Assert parent selection where the cost scenarios actually specify it
Four scenarios exist to test cost-based parent selection and each named
its expected outcome in a comment that nothing read. Add a tree_parents
assertion mapping a node to the parent it must have in the final tree
snapshot, and encode it for the two scenarios whose stated outcome the
implementation meets: cost-avoidance (n04 takes the fiber n03) and
bottleneck-parent (n06 takes the fiber n03, n09 keeps its only parent
n05). Both hold in all six provably-completed archived runs.

The other two are left unasserted on purpose, and each for a different
reason worth keeping distinct.

mixed-technology says n06 and n08 should both pick the fiber parent n03.
They do not. Across the five completed archived runs n06 picks n10 three
times and n08 picks n04 four times. Encoding the criterion as written
would red the scenario most runs, and encoding the observed behaviour
would bless something nobody specified, so the disagreement is recorded
at the site as an open question. n06 preferring n10 may well be correct
and the comment stale, since n10 reaches it by fiber too.

depth-vs-cost is different: its validation line does not name an outcome
at all, saying only that the choice "reflects the actual cost tradeoff",
which either answer satisfies. The corpus shows both occurring under one
seed, three runs to two. That scenario needs a protocol decision about
which parent is correct before it can have an assertion.

Compare parents by address resolved from the snapshot's own
my_node_addr, and fail rather than skip when a node is absent from the
snapshot or still claims to be its own root. Those two states are the
common ones in the older corpus and both produce the same "no match" a
wrong parent does, so only separating them keeps a harness problem from
reading as a routing verdict.
2026-07-23 07:05:50 +00:00
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