test(usage-log): add unit tests for recordTokenUsage IO fields

src/agents/usage-log.test.ts

@@ -0,0 +1,116 @@
+import { describe, expect, it, beforeEach, afterEach } from "vitest";
+import fs from "fs/promises";
+import path from "path";
+import os from "os";
+import { recordTokenUsage } from "./usage-log.js";
+
+describe("recordTokenUsage", () => {
+  let tmpDir: string;
+  let usageFile: string;
+
+  beforeEach(async () => {
+    tmpDir = await fs.mkdtemp(path.join(os.tmpdir(), "usage-log-test-"));
+    usageFile = path.join(tmpDir, "memory", "token-usage.json");
+  });
+
+  afterEach(async () => {
+    await fs.rm(tmpDir, { recursive: true, force: true });
+  });
+
+  it("writes inputTokens and outputTokens when provided", async () => {
+    await recordTokenUsage({
+      workspaceDir: tmpDir,
+      label: "llm_output",
+      model: "claude-sonnet-4-6",
+      provider: "anthropic",
+      usage: { input: 1000, output: 500, total: 1500 },
+    });
+
+    const records = JSON.parse(await fs.readFile(usageFile, "utf-8"));
+    expect(records).toHaveLength(1);
+    expect(records[0].tokensUsed).toBe(1500);
+    expect(records[0].inputTokens).toBe(1000);
+    expect(records[0].outputTokens).toBe(500);
+    expect(records[0].cacheReadTokens).toBeUndefined();
+    expect(records[0].cacheWriteTokens).toBeUndefined();
+  });
+
+  it("writes cacheReadTokens and cacheWriteTokens when provided", async () => {
+    await recordTokenUsage({
+      workspaceDir: tmpDir,
+      label: "llm_output",
+      usage: { input: 800, output: 200, cacheRead: 300, cacheWrite: 100, total: 1400 },
+    });
+
+    const records = JSON.parse(await fs.readFile(usageFile, "utf-8"));
+    expect(records[0].inputTokens).toBe(800);
+    expect(records[0].outputTokens).toBe(200);
+    expect(records[0].cacheReadTokens).toBe(300);
+    expect(records[0].cacheWriteTokens).toBe(100);
+  });
+
+  it("omits IO fields when usage only has total (legacy records)", async () => {
+    await recordTokenUsage({
+      workspaceDir: tmpDir,
+      label: "llm_output",
+      usage: { total: 28402 },
+    });
+
+    const records = JSON.parse(await fs.readFile(usageFile, "utf-8"));
+    expect(records[0].tokensUsed).toBe(28402);
+    expect(records[0].inputTokens).toBeUndefined();
+    expect(records[0].outputTokens).toBeUndefined();
+  });
+
+  it("skips writing when usage is undefined", async () => {
+    await recordTokenUsage({
+      workspaceDir: tmpDir,
+      label: "llm_output",
+      usage: undefined,
+    });
+
+    const exists = await fs.access(usageFile).then(() => true).catch(() => false);
+    expect(exists).toBe(false);
+  });
+
+  it("skips writing when total is zero", async () => {
+    await recordTokenUsage({
+      workspaceDir: tmpDir,
+      label: "llm_output",
+      usage: { input: 0, output: 0 },
+    });
+
+    const exists = await fs.access(usageFile).then(() => true).catch(() => false);
+    expect(exists).toBe(false);
+  });
+
+  it("appends multiple records to the same file", async () => {
+    await recordTokenUsage({
+      workspaceDir: tmpDir,
+      label: "llm_output",
+      usage: { input: 100, output: 50, total: 150 },
+    });
+    await recordTokenUsage({
+      workspaceDir: tmpDir,
+      label: "llm_output",
+      usage: { input: 200, output: 80, total: 280 },
+    });
+
+    const records = JSON.parse(await fs.readFile(usageFile, "utf-8"));
+    expect(records).toHaveLength(2);
+    expect(records[0].inputTokens).toBe(100);
+    expect(records[1].inputTokens).toBe(200);
+  });
+
+  it("truncates fractional tokens", async () => {
+    await recordTokenUsage({
+      workspaceDir: tmpDir,
+      label: "llm_output",
+      usage: { input: 100.9, output: 50.1, total: 151 },
+    });
+
+    const records = JSON.parse(await fs.readFile(usageFile, "utf-8"));
+    expect(records[0].inputTokens).toBe(100);
+    expect(records[0].outputTokens).toBe(50);
+  });
+});