test: add frontend test suite

src/test/setup.ts

@@ -0,0 +1,49 @@
+import "@testing-library/jest-dom/vitest";
+import { afterEach, beforeEach, vi } from "vitest";
+import { cleanup } from "@testing-library/react";
+
+function createLocalStorageMock(): Storage {
+  let store: Record<string, string> = {};
+  return {
+    get length() {
+      return Object.keys(store).length;
+    },
+    clear() {
+      store = {};
+    },
+    getItem(key: string) {
+      return Object.prototype.hasOwnProperty.call(store, key)
+        ? store[key]
+        : null;
+    },
+    key(index: number) {
+      return Object.keys(store)[index] ?? null;
+    },
+    removeItem(key: string) {
+      delete store[key];
+    },
+    setItem(key: string, value: string) {
+      store[key] = String(value);
+    },
+  };
+}
+
+beforeEach(() => {
+  const storage = createLocalStorageMock();
+  Object.defineProperty(globalThis, "localStorage", {
+    value: storage,
+    configurable: true,
+  });
+  Object.defineProperty(window, "localStorage", {
+    value: storage,
+    configurable: true,
+  });
+});
+
+afterEach(() => {
+  cleanup();
+  globalThis.localStorage.clear();
+  vi.restoreAllMocks();
+  vi.unstubAllGlobals();
+  vi.unstubAllEnvs();
+});