app/test/setup.ts

@@ -2,6 +2,22 @@ import '@testing-library/jest-dom';
 import { cleanup } from '@testing-library/react';
 import { afterEach, vi } from 'vitest';
 
+// Radix UI / @floating-ui calls requestAnimationFrame for layout and
+// positioning on every render (Popover, DropdownMenu, Checkbox focus rings,
+// etc.).  In jsdom those callbacks are deferred to a future tick, landing
+// outside the current act() boundary.  React queues the resulting state
+// updates, which schedule more microtasks, and the act() settlement loop
+// keeps running until Vitest's 5000ms hard timeout kills the test.
+//
+// Making rAF synchronous keeps every callback inside the current act() cycle
+// so there are no pending tasks when the test finishes.  This fixes the whole
+// class of flaky timeouts without touching individual test files.
+global.requestAnimationFrame = (cb: FrameRequestCallback): number => {
+  cb(performance.now());
+  return 0;
+};
+global.cancelAnimationFrame = (_id: number): void => {};
+
 // Cleanup after each test
 afterEach(() => {
   cleanup();