feat(stats): aggregate token/cost totals in cache-analyzer

tests/lib/cache-analyzer.test.mjs

@@ -0,0 +1,78 @@
+// tests/lib/cache-analyzer.test.mjs
+// SKAL-2 Step 3 — token/cost aggregation in cache-analyzer's summarize().
+// Also the first test coverage for cache-analyzer (previously zero-coverage):
+// includes a regression guard that the pre-existing duration/event-name fields
+// still compute correctly on mixed input.
+//
+// Hermetic: no LLM, network, time, or randomness. Idiom:
+// tests/lib/token-usage.test.mjs (pure-module node:test style).
+
+import { test } from 'node:test';
+import { strict as assert } from 'node:assert';
+import { summarize } from '../../lib/stats/cache-analyzer.mjs';
+
+const jsonl = (objs) => objs.map(o => JSON.stringify(o));
+
+// ---- token/cost aggregation ------------------------------------------------
+
+test('summarize — two token-bearing records → summed totals + cost', () => {
+  const s = summarize(jsonl([
+    { ts: '2026-06-26T12:00:00Z', session_id: 'S1', scope: 'main-context', tokens_input: 1000, tokens_output: 200, tokens_cache_creation: 400, tokens_cache_read: 5000, cost_usd: 0.03675 },
+    { ts: '2026-06-26T13:00:00Z', session_id: 'S2', scope: 'main-context', tokens_input: 2000, tokens_output: 300, tokens_cache_creation: 600, tokens_cache_read: 1000, cost_usd: 0.05 },
+  ]));
+  assert.equal(s.total_tokens_input, 3000);
+  assert.equal(s.total_tokens_output, 500);
+  assert.equal(s.total_tokens_cache_creation, 1000);
+  assert.equal(s.total_tokens_cache_read, 6000);
+  assert.equal(s.sessions_with_tokens, 2);
+  assert.ok(Math.abs(s.total_cost_usd - 0.08675) < 1e-9, `cost ${s.total_cost_usd}`);
+});
+
+test('summarize — cost_usd:null counts the session but is excluded from total_cost_usd', () => {
+  const s = summarize(jsonl([
+    { session_id: 'S1', tokens_input: 100, cost_usd: 0.01 },
+    { session_id: 'S2', tokens_input: 200, cost_usd: null, is_estimate: true },
+  ]));
+  assert.equal(s.sessions_with_tokens, 2, 'null-cost session must still be counted');
+  assert.equal(s.total_tokens_input, 300);
+  assert.ok(Math.abs(s.total_cost_usd - 0.01) < 1e-9, `cost ${s.total_cost_usd}`);
+});
+
+test('summarize — no token records → token totals stay zero (additive default)', () => {
+  const s = summarize(jsonl([
+    { event: 'main-merge-gate', duration_ms: 100 },
+  ]));
+  assert.equal(s.total_tokens_input, 0);
+  assert.equal(s.total_cost_usd, 0);
+  assert.equal(s.sessions_with_tokens, 0);
+});
+
+// ---- regression guard: pre-existing fields still computed ------------------
+
+test('summarize — existing duration/event-name fields still correct on mixed input', () => {
+  const s = summarize(jsonl([
+    { event: 'main-merge-gate', duration_ms: 100, ts: '2026-06-26T10:00:00Z' },
+    { event: 'main-merge-approved', duration_ms: 200, ts: '2026-06-26T11:00:00Z' },
+    { session_id: 'S1', tokens_input: 1000, cost_usd: 0.04, ts: '2026-06-26T12:00:00Z' },
+  ]));
+  // Pre-existing behavior (regression guard)
+  assert.equal(s.total_events, 3);
+  assert.equal(s.events_with_duration, 2);
+  assert.equal(s.wall_time_ms_max, 200);
+  assert.deepEqual(s.unique_event_names, ['main-merge-approved', 'main-merge-gate']);
+  // New behavior coexists
+  assert.equal(s.total_tokens_input, 1000);
+  assert.equal(s.sessions_with_tokens, 1);
+  assert.ok(Math.abs(s.total_cost_usd - 0.04) < 1e-9);
+});
+
+test('summarize — malformed/empty lines tolerated alongside token records', () => {
+  const s = summarize([
+    '',
+    'not json',
+    JSON.stringify({ session_id: 'S1', tokens_input: 50, cost_usd: 0.001 }),
+  ]);
+  assert.equal(s.total_events, 1);
+  assert.equal(s.sessions_with_tokens, 1);
+  assert.equal(s.total_tokens_input, 50);
+});