improved component composition and added tests.

src/test/setup.ts

@@ -0,0 +1,22 @@
+import '@testing-library/jest-dom/vitest'
+
+const values = new Map<string, string>()
+const memoryStorage: Storage = {
+  get length() {
+    return values.size
+  },
+  clear: () => values.clear(),
+  getItem: (key) => values.get(key) ?? null,
+  key: (index) => [...values.keys()][index] ?? null,
+  removeItem: (key) => {
+    values.delete(key)
+  },
+  setItem: (key, value) => {
+    values.set(key, String(value))
+  },
+}
+
+Object.defineProperty(globalThis, 'localStorage', {
+  configurable: true,
+  value: memoryStorage,
+})