test(priceOracle): unit tests for median, anomaly detection, and aggregation

[storm-beyndtech]

Summary

Adds unit test coverage for the core price oracle business logic in
src/services/priceOracle.js — median aggregation, temporal anomaly
detection, and multi-source fan-out. Closes #7.

Coverage for priceOracle.js: 98% (acceptance gate is 80%). The suite
mocks cache, the three price sources, config, and logger, so it needs
no external services.

Heads-up for the reviewer

• A latent bug surfaced while writing these tests and is fixed here.
  fetchFreshPrice mapped a non-existent .name field over source results
  (which expose .source), so sources_attempted was always
  [undefined, …] on every fresh fetch — and that value was cached and
  served. It was never filed because the existing test/prices.test.js stubs
  the whole oracle, so this line had never run under assertion. Fixed in the
  same change since it lives in the function under test.
• detectAnomaly is temporal and log-only. It compares the current
  aggregate against the last cached aggregate over time; it does not
  exclude an outlier source from the median, and its return value is
  discarded by fetchFreshPrice. The tests document this actual behavior
  rather than an assumed cross-source rejection scheme.

Changes

• test/priceOracle.test.js — 34 tests:
  • median — empty/single/even/odd, non-mutation, numeric (not lexical)
    sort, single-outlier resistance
  • detectAnomaly — no-history, below / at / above the strict-> 20%
    threshold, symmetric down-moves, re-store-on-anomaly, issuer-scoped keys,
    cache read/write failure branches
  • fetchFromAllSources — all-succeed, partial failure, all-fail, null/zero
    filtering, single healthy source (no quorum rule)
  • getPrice — cache hit (fresh + stale is_stale flag), cache miss →
    fresh fetch + write-back, cache-read-throw → redis_unavailable
  • fetchFreshPrice — unavailable shape, anomaly path, redisUnavailable
    short-circuit, write-fail degradation
  • refreshAllCachedPrices — not-connected skip, scan + refresh (history
    keys excluded), scan-throw abort
• src/services/priceOracle.js
  • Export median / detectAnomaly / fetchFromAllSources for unit testing
  • Fix r.name → r.source in fetchFreshPrice (the bug above)
• .gitignore — ignore generated coverage/ output

Test suite note

The repository's broader suite has pre-existing failures that require Redis /
Postgres (and a config.test.js that spawns subprocesses). For reference:

	Failed suites	Failed tests
main (baseline)	19	25
this branch	18	2

The branch is strictly better, and none of the remaining failures are
introduced here. The new priceOracle suite passes fully on its own.

Acceptance criteria

• Test runner with npm test (Jest — already configured)
• median fully tested (edge cases included)
• detectAnomaly tested below/at/above threshold
• fetchFromAllSources tested with partial failures
• getPrice tested for cache hit and miss paths
• Coverage ≥ 80% for priceOracle.js (98%)