Most of what remained on #26.
**Property tests (`tests/properties.rs`, proptest as a dev-dependency).** Four
invariants over generated 1v1 schedules rather than hand-written fixtures,
which is where this crate's shipped defects actually hid — a linear evidence
product that underflowed only past ~1000 teams, and a batching path no golden
exercised because every golden ingests in one call:
- converged posteriors are always finite with positive sigma
- log-evidence, batch and filtered, is finite and never above zero
- filtered evidence is invariant to whether `converge` has run
- one-at-a-time ingestion reaches the same fixed point as batched
The invariance property was mutation-proved: making `filtered_step` read
`skill.forward` instead of the carried message fails it with
`-1.1038430064192069 -> -1.1135747072822761`.
**Shared finiteness helper (`tests/common/mod.rs`).** `assert_finite` was local
to `degenerate_inputs.rs`. It now also rejects a non-positive sigma, which the
old version let through — `Gaussian::sigma` reports a non-positive precision as
improper rather than trapping, so a collapsed posterior would have passed a
finite-only check.
**Boundary inputs.** Zero and negative weights, out-of-order timestamps, and
extreme beta/sigma combinations. Worth recording that zero weight reaches
`(m - performance.exclude(..)) * (1.0 / w)` — a division by zero — and the
posterior comes out finite anyway; the test pins that rather than asserting
what ought to happen. The weight tests `expect()` the commit rather than
returning early on error, because an early return would have made them vacuous
the moment validation changed. I checked that specifically by turning the
return into a failure and confirming it did not fire.
Not done, and left on #26: benchmark regression gating. Nothing fails on a
regression today; making it fail needs a threshold chosen against how noisy the
shared runner is, which is a policy call rather than a mechanical one.
60 test binaries, up from 56. MSRV 1.85 verified with proptest in the graph.
Co-Authored-By: Claude Opus 5 (1M context) <noreply@anthropic.com>
Claude-Session: https://claude.ai/code/session_01T5SYDExxL4vZgvunrcNSMc
