fix(web): isolate unit test storage (#33021)

web/test/unit/mocks/storage.ts

@@ -0,0 +1,27 @@
+export class MemoryStorage implements Storage {
+  private items = new Map<string, string>();
+
+  get length() {
+    return this.items.size;
+  }
+
+  key(index: number) {
+    return [...this.items.keys()][index] ?? null;
+  }
+
+  getItem(key: string) {
+    return this.items.get(key) ?? null;
+  }
+
+  setItem(key: string, value: string) {
+    this.items.set(key, value);
+  }
+
+  removeItem(key: string) {
+    this.items.delete(key);
+  }
+
+  clear() {
+    this.items.clear();
+  }
+}

web/test/unit/setup.ts

@@ -1,5 +1,10 @@
+import { MemoryStorage } from '#test/unit/mocks/storage.ts';
 import { init } from 'svelte-i18n';
 
+for (const name of ['localStorage', 'sessionStorage']) {
+  Object.defineProperty(globalThis, name, { value: new MemoryStorage(), configurable: true });
+}
+
 beforeAll(async () => {
   await init({ fallbackLocale: 'dev' });
 });