documentation update

docs/reference/testing.md

@@ -18,6 +18,7 @@ npm test          # = node --test  (discovers test/*.test.js at the repo root)
 | `test/summarization.test.js` | Summarization decision logic | `maybeSummarize` (orchestration) |
 | `test/entity-extraction.test.js` | Greeting + regurgitation guards | `mentionedIn`, `isIgnoredName` (memory-service) |
 | `test/schema.test.js` | Fresh-DB schema completeness | `schema.js` string (memory-service) |
+| `test/trivial-turn.test.js` | Greeting/trivial-turn detection | `isTrivialTurn` (shared) |
 | `test/migrations.test.js` | Migration version-stepping | `migrate` (memory-service) |
 
 Tests import the **real** functions rather than reimplementing logic — the
@@ -44,3 +45,10 @@ Keep the pattern: export the real function, import it, mock I/O at the boundary
 logic (ranking, tokenizing, version-stepping, decision branches) over wiring.
 Several of these tests were written *after* a bug slipped through — each new
 class of mistake is worth a case so it can't recur silently.
+
+When a mocked service call changes shape (e.g. the `utilityInference` refactor
+moving summarization from Ollama's `/api/generate` to the inference service's
+`/utility/complete`), the mock URL router must move with it — an "unexpected
+fetch" throw in these tests usually means the code under test evolved, not
+broke. Runner-contract tests (migrations) inject stub no-op migration arrays
+rather than letting the real SQL-bearing migrations hit the minimal fake db.