diff --git a/vitest.setup.ts b/vitest.setup.ts
index d2973f28..fe2c426f 100644
--- a/vitest.setup.ts
+++ b/vitest.setup.ts
@@ -14,3 +14,20 @@ Object.defineProperty(window, 'matchMedia', {
     dispatchEvent: () => false,
   }),
 })
+
+if (typeof window !== 'undefined') {
+  if (!window.localStorage || typeof window.localStorage.clear !== 'function') {
+    let store: Record<string, string> = {};
+    const mockLocalStorage = {
+      getItem: (key: string) => store[key] || null,
+      setItem: (key: string, value: string) => { store[key] = String(value); },
+      removeItem: (key: string) => { delete store[key]; },
+      clear: () => { store = {}; },
+      length: 0,
+      key: (index: number) => Object.keys(store)[index] || null,
+    };
+    Object.defineProperty(window, 'localStorage', { value: mockLocalStorage, writable: true });
+    Object.defineProperty(globalThis, 'localStorage', { value: mockLocalStorage, writable: true });
+  }
+}
+