test(memory): share short-timeout test helper

test/helpers/fast-short-timeouts.ts

@@ -0,0 +1,17 @@
+import { vi } from "vitest";
+
+export function useFastShortTimeouts(maxDelayMs = 2000): () => void {
+  const realSetTimeout = setTimeout;
+  const spy = vi.spyOn(global, "setTimeout").mockImplementation(((
+    handler: TimerHandler,
+    timeout?: number,
+    ...args: unknown[]
+  ) => {
+    const delay = typeof timeout === "number" ? timeout : 0;
+    if (delay > 0 && delay <= maxDelayMs) {
+      return realSetTimeout(handler, 0, ...args);
+    }
+    return realSetTimeout(handler, delay, ...args);
+  }) as typeof setTimeout);
+  return () => spy.mockRestore();
+}