fix(FN-4388): tighten cache-stats ephemeral filtering and tests

Fusion-Task-Id: FN-4388
Fusion-Task-Lineage: 7497a0a1-5edb-4778-b339-118d1fd668f7

scripts/__tests__/cache-stats.test.mjs

@@ -1,6 +1,6 @@
 import test from "node:test";
 import assert from "node:assert/strict";
-import { collectCacheStats } from "../cache-stats.mjs";
+import { collectCacheStats, main } from "../cache-stats.mjs";
 
 test("collectCacheStats groups role and permanent-agent totals", async () => {
   const taskStore = {
@@ -21,7 +21,11 @@ test("collectCacheStats groups role and permanent-agent totals", async () => {
     },
   };
 
-  const result = await collectCacheStats({ taskStore, agentStore });
+  const result = await collectCacheStats({
+    taskStore,
+    agentStore,
+    isEphemeralAgent: (agent) => agent.metadata?.type === "spawned" || agent.metadata?.agentKind === "task-worker",
+  });
 
   assert.equal(result.byRole.find((r) => r.role === "executor")?.total_cached, 50);
   assert.equal(result.byRole.find((r) => r.role === "reviewer")?.total_input, 200);
@@ -30,3 +34,33 @@ test("collectCacheStats groups role and permanent-agent totals", async () => {
   assert.equal(result.byAgent[0].id, "a1");
   assert.equal(result.byAgent[0].hit_ratio, 50 / 150);
 });
+
+test("collectCacheStats handles empty and zero-token datasets", async () => {
+  const taskStore = { async listTasks() { return [{ assignedAgentId: "a1" }, { assignedAgentId: "a1", tokenUsage: { inputTokens: 0, cachedTokens: 0, cacheWriteTokens: 0, outputTokens: 0 } }]; } };
+  const agentStore = { async listAgents() { return [{ id: "a1", role: "executor", metadata: { type: "permanent" } }]; } };
+
+  const result = await collectCacheStats({ taskStore, agentStore, isEphemeralAgent: () => false });
+  assert.equal(result.byRole.length, 1);
+  assert.equal(result.byRole[0].hit_ratio, 0);
+  assert.equal(result.byAgent[0].n_tasks, 1);
+});
+
+test("main --json prints machine-readable output", async () => {
+  const logs = [];
+  const originalLog = console.log;
+  console.log = (value) => logs.push(String(value));
+  try {
+    const code = await main(["--json"], {
+      stores: {
+        taskStore: { async listTasks() { return []; } },
+        agentStore: { async listAgents() { return []; } },
+        isEphemeralAgent: () => false,
+      },
+    });
+    assert.equal(code, 0);
+    const parsed = JSON.parse(logs[0]);
+    assert.deepEqual(parsed, { byRole: [], byAgent: [] });
+  } finally {
+    console.log = originalLog;
+  }
+});