refactor(common): fix viewport tests

JeanMeche · amishne · commit 42d57c35781f · 2026-04-28T16:38:11.000-07:00
10ad3c0 broke the 21.2.x branch
diff --git a/packages/common/test/viewport_scroller_spec.ts b/packages/common/test/viewport_scroller_spec.ts
@@ -6,8 +6,8 @@
  * found in the LICENSE file at https://angular.dev/license
  */
 
-import {BrowserViewportScroller, ViewportScroller} from '../src/viewport_scroller';
 import {isNode, waitFor} from '@angular/private/testing';
+import {BrowserViewportScroller, ViewportScroller} from '../src/viewport_scroller';
 
 describe('BrowserViewportScroller', () => {
   describe('setHistoryScrollRestoration', () => {
diff --git a/packages/private/testing/src/utils.ts b/packages/private/testing/src/utils.ts
@@ -209,3 +209,50 @@ export function useAutoTick() {
     jasmine.clock().uninstall();
   });
 }
+
+export interface WaitForOptions {
+  timeout?: number;
+  interval?: number;
+}
+
+// Intentionally does not participate in fake clocks.
+const realNow = performance.now.bind(performance);
+const realSetTimeout = setTimeout;
+
+export async function waitFor<T>(
+  callback: () => Promise<T> | T,
+  options: WaitForOptions = {},
+): Promise<T> {
+  const waitTime = options.timeout ?? 100;
+  const interval = options.interval ?? 0;
+  const stack = new Error().stack;
+
+  const deadline = realNow() + waitTime;
+  let i = 0;
+  let lastError: any | undefined;
+
+  while (true) {
+    try {
+      return await callback();
+    } catch (cause) {
+      lastError = cause;
+    }
+
+    i++;
+
+    if (deadline < realNow()) {
+      throw Object.assign(
+        new Error(
+          `Timed out after ${waitTime}ms and ${i} attempts. ` +
+            `Last error: ${lastError?.message ?? 'condition returned false'}`,
+        ),
+        {
+          stack: stack + `Last error: ${lastError?.stack ?? 'condition returned false'}`,
+        },
+      );
+    }
+
+    // Guarantee a macro-task between retries.
+    await new Promise((resolve) => void realSetTimeout(resolve, interval));
+  }
+}
