🧪 test(auth): add error handling tests for loadSession

src/auth/session-store.test.ts

@@ -0,0 +1,46 @@
+import assert from "node:assert/strict";
+import { describe, it, vi } from "vitest";
+import { loadSession } from "./session-store.js";
+
+vi.mock("node:fs/promises", async (importOriginal) => {
+  const mod = await importOriginal<typeof import("node:fs/promises")>();
+  return {
+    ...mod,
+    readFile: vi.fn(mod.readFile),
+  };
+});
+
+import { readFile } from "node:fs/promises";
+import { sessionFilePath } from "../config/paths.js";
+
+describe("loadSession", () => {
+  it("returns null when the session file is missing (ENOENT)", async () => {
+    vi.mocked(readFile).mockRejectedValueOnce(
+      Object.assign(new Error("File not found"), { code: "ENOENT" }),
+    );
+
+    const session = await loadSession();
+    assert.equal(session, null);
+  });
+
+  it("throws non-ENOENT errors when reading the session file fails", async () => {
+    vi.mocked(readFile).mockRejectedValueOnce(
+      Object.assign(new Error("Permission denied"), { code: "EACCES" }),
+    );
+
+    await assert.rejects(loadSession(), /Permission denied/);
+  });
+
+  it("returns the parsed session when the file exists and is valid", async () => {
+    const fakeSession = {
+      browserbaseSessionId: "fake-id",
+      publicationUrl: "https://example.substack.com",
+      createdAt: "2023-01-01T00:00:00.000Z",
+      updatedAt: "2023-01-01T00:00:00.000Z",
+    };
+    vi.mocked(readFile).mockResolvedValueOnce(JSON.stringify(fakeSession));
+
+    const session = await loadSession();
+    assert.deepEqual(session, fakeSession);
+  });
+});