feat: mock localStorage for tests

Author: Synogun

tests/setup/vitest.setup.ts

@@ -1,9 +1,32 @@
-import { afterEach, beforeEach } from 'vitest';
+import { afterAll, beforeEach, vi } from 'vitest';
+
+const localStorageMock: Storage = (() => {
+    const store = new Map<string, string>();
+
+    return {
+        getItem: (key: string) => store.get(key) ?? null,
+        setItem: (key: string, value: string) => {
+            store.set(key, value);
+        },
+        removeItem: (key: string) => {
+            store.delete(key);
+        },
+        clear: () => {
+            store.clear();
+        },
+        get length() {
+            return store.size;
+        },
+        key: (index: number) => Array.from(store.keys())[index] ?? null,
+    };
+})();
+
+vi.stubGlobal('localStorage', localStorageMock);
 
 beforeEach(() => {
-    // Reserved for shared test setup.
+    localStorage.clear();
 });
 
-afterEach(() => {
-    // Reserved for shared test cleanup.
-});
+afterAll(() => {
+    vi.unstubAllGlobals();
+});