test: add debug logger unit coverage

tests/output/debug.test.ts

@@ -0,0 +1,106 @@
+import path from "node:path";
+import { jest } from "@jest/globals";
+
+const appendFileSyncMock = jest.fn<any>();
+
+jest.unstable_mockModule("node:fs", () => ({
+  default: {
+    appendFileSync: appendFileSyncMock,
+  },
+  appendFileSync: appendFileSyncMock,
+}));
+
+let createDebugLogger: typeof import("../../src/output/debug.js").createDebugLogger;
+
+beforeAll(async () => {
+  ({ createDebugLogger } = await import("../../src/output/debug.js"));
+});
+
+beforeEach(() => {
+  jest.clearAllMocks();
+  jest.useFakeTimers();
+  jest.setSystemTime(new Date("2026-08-23T06:00:00.000Z"));
+});
+
+afterEach(() => {
+  jest.restoreAllMocks();
+  jest.useRealTimers();
+});
+
+describe("createDebugLogger", () => {
+  it("keeps disabled sessions from writing or announcing", () => {
+    const consoleErrorSpy = jest.spyOn(console, "error").mockImplementation(() => {});
+
+    const debug = createDebugLogger(false);
+    debug.log("ignored", { reason: "disabled" });
+    debug.announcePath();
+    debug.close();
+
+    expect(appendFileSyncMock).not.toHaveBeenCalled();
+    expect(consoleErrorSpy).not.toHaveBeenCalled();
+  });
+
+  it("writes enabled log messages to the timestamped debug file", () => {
+    const debug = createDebugLogger(true);
+
+    debug.log("cache hit");
+    debug.close();
+
+    expect(appendFileSyncMock).toHaveBeenCalledWith(
+      path.join(process.cwd(), "cve-lite-debug-2026-08-23T06-00-00.log"),
+      "2026-08-23T06:00:00.000Z [debug] cache hit\n",
+      "utf8",
+    );
+  });
+
+  it("announces the debug path only once", () => {
+    const consoleErrorSpy = jest.spyOn(console, "error").mockImplementation(() => {});
+    const debug = createDebugLogger(true);
+
+    debug.announcePath();
+    debug.announcePath();
+
+    expect(consoleErrorSpy).toHaveBeenCalledTimes(1);
+    expect(consoleErrorSpy).toHaveBeenCalledWith(
+      "[debug] Writing debug log to ./cve-lite-debug-2026-08-23T06-00-00.log",
+    );
+  });
+
+  it("writes string details without JSON quoting", () => {
+    const debug = createDebugLogger(true);
+
+    debug.log("request", "plain text");
+
+    expect(appendFileSyncMock).toHaveBeenCalledWith(
+      expect.any(String),
+      "2026-08-23T06:00:00.000Z [debug] request plain text\n",
+      "utf8",
+    );
+  });
+
+  it("serializes object details as JSON", () => {
+    const debug = createDebugLogger(true);
+
+    debug.log("request", { method: "GET", cached: true });
+
+    expect(appendFileSyncMock).toHaveBeenCalledWith(
+      expect.any(String),
+      '2026-08-23T06:00:00.000Z [debug] request {"method":"GET","cached":true}\n',
+      "utf8",
+    );
+  });
+
+  it("falls back to string conversion for circular details", () => {
+    const details: { self?: unknown } = {};
+    details.self = details;
+    const debug = createDebugLogger(true);
+
+    debug.log("request", details);
+
+    expect(appendFileSyncMock).toHaveBeenCalledWith(
+      expect.any(String),
+      "2026-08-23T06:00:00.000Z [debug] request [object Object]\n",
+      "utf8",
+    );
+  });
+});