[Tests] add unit tests for accounts (#2748)

* add unit tests for accounts

* only import from vitest (not node:test)

* resolve comments

* improve test coverage for accounts.updateUserInfo

* add test coverage for account.initLoggedInUser()

* code style improvements

src/test/account.spec.ts

@@ -0,0 +1,74 @@
+import * as battleScene from "#app/battle-scene.js";
+import { describe, expect, it, vi } from "vitest";
+import { initLoggedInUser, loggedInUser, updateUserInfo } from "../account";
+import * as utils from "../utils";
+
+describe("account", () => {
+  describe("initLoggedInUser", () => {
+    it("should set loggedInUser to Guest and lastSessionSlot to -1", () => {
+      initLoggedInUser();
+
+      expect(loggedInUser.username).toBe("Guest");
+      expect(loggedInUser.lastSessionSlot).toBe(-1);
+    });
+  });
+
+  describe("updateUserInfo", () => {
+    it("should set loggedInUser to Guest if bypassLogin is true", async () => {
+      vi.spyOn(battleScene, "bypassLogin", "get").mockReturnValue(true);
+
+      const [success, status] = await updateUserInfo();
+
+      expect(success).toBe(true);
+      expect(status).toBe(200);
+      expect(loggedInUser.username).toBe("Guest");
+      expect(loggedInUser.lastSessionSlot).toBe(-1);
+    });
+
+    it("should fetch user info from the API if bypassLogin is false", async () => {
+      vi.spyOn(battleScene, "bypassLogin", "get").mockReturnValue(false);
+      vi.spyOn(utils, "apiFetch").mockResolvedValue(
+        new Response(
+          JSON.stringify({
+            username: "test",
+            lastSessionSlot: 99,
+          }),
+          {
+            status: 200,
+          }
+        )
+      );
+
+      const [success, status] = await updateUserInfo();
+
+      expect(success).toBe(true);
+      expect(status).toBe(200);
+      expect(loggedInUser.username).toBe("test");
+      expect(loggedInUser.lastSessionSlot).toBe(99);
+    });
+
+    it("should handle resolved API errors", async () => {
+      vi.spyOn(battleScene, "bypassLogin", "get").mockReturnValue(false);
+      vi.spyOn(utils, "apiFetch").mockResolvedValue(
+        new Response(null, { status: 401 })
+      );
+
+      const [success, status] = await updateUserInfo();
+
+      expect(success).toBe(false);
+      expect(status).toBe(401);
+    });
+
+    it("should handle rejected API errors", async () => {
+      const consoleErrorSpy = vi.spyOn(console, "error");
+      vi.spyOn(battleScene, "bypassLogin", "get").mockReturnValue(false);
+      vi.spyOn(utils, "apiFetch").mockRejectedValue(new Error("Api failed!"));
+
+      const [success, status] = await updateUserInfo();
+
+      expect(success).toBe(false);
+      expect(status).toBe(500);
+      expect(consoleErrorSpy).toHaveBeenCalled();
+    });
+  });
+});