test(local-storage): add unit tests

tests/LocalStorage/LocalStorageObject.test.ts

@@ -0,0 +1,58 @@
+import { render } from "@testing-library/svelte";
+import LocalStorageObject from "./LocalStorageObject.test.svelte";
+
+describe("LocalStorage - Object Values", () => {
+  let localStorageMock: { [key: string]: string };
+  let originalLocalStorage: Storage;
+
+  beforeEach(() => {
+    originalLocalStorage = global.localStorage;
+    localStorageMock = {};
+
+    global.localStorage = {
+      getItem: vi.fn((key) => localStorageMock[key] || null),
+      setItem: vi.fn((key, value) => {
+        localStorageMock[key] = value;
+      }),
+      removeItem: vi.fn((key) => {
+        delete localStorageMock[key];
+      }),
+      clear: vi.fn(() => {
+        localStorageMock = {};
+      }),
+      length: 0,
+      key: vi.fn(),
+    };
+  });
+
+  afterEach(() => {
+    global.localStorage = originalLocalStorage;
+    localStorage.clear();
+    vi.restoreAllMocks();
+    localStorageMock = {};
+  });
+
+  it("saves object value as JSON string", () => {
+    render(LocalStorageObject);
+
+    expect(localStorage.setItem).toHaveBeenCalledWith(
+      "theme-settings",
+      JSON.stringify({ theme: "dark", fontSize: 16 }),
+    );
+  });
+
+  it("loads existing object value from localStorage", () => {
+    const existingSettings = { theme: "light", fontSize: 14 };
+    localStorageMock["theme-settings"] = JSON.stringify(existingSettings);
+
+    render(LocalStorageObject);
+    expect(localStorage.getItem).toHaveBeenCalledWith("theme-settings");
+  });
+
+  it("handles malformed JSON gracefully", () => {
+    localStorageMock["theme-settings"] = "{malformed-json}";
+
+    render(LocalStorageObject);
+    expect(localStorage.getItem).toHaveBeenCalledWith("theme-settings");
+  });
+});