Fix tests to wrap all calls changing the UI with act. (#12268)

packages/cli/src/test-utils/async.ts

@@ -0,0 +1,34 @@
+/**
+ * @license
+ * Copyright 2025 Google LLC
+ * SPDX-License-Identifier: Apache-2.0
+ */
+
+import { act } from 'react';
+
+// The waitFor from vitest doesn't properly wrap in act(), so we have to
+// implement our own like the one in @testing-library/react
+// or @testing-library/react-native
+// The version of waitFor from vitest is still fine to use if you aren't waiting
+// for React state updates.
+export async function waitFor(
+  assertion: () => void,
+  { timeout = 1000, interval = 50 } = {},
+): Promise<void> {
+  const startTime = Date.now();
+
+  while (true) {
+    try {
+      assertion();
+      return;
+    } catch (error) {
+      if (Date.now() - startTime > timeout) {
+        throw error;
+      }
+
+      await act(async () => {
+        await new Promise((resolve) => setTimeout(resolve, interval));
+      });
+    }
+  }
+}