test for scroll stuff

Author: shakyShane

special-pages/pages/new-tab/integration-tests/new-tab.page.js

@@ -189,6 +189,39 @@ export class NewtabPage {
             await this.mocks.simulateSubscriptionMessage(sub('tabs_onDataUpdate'), tabs({ tabId, tabIds }));
         });
     }
+
+    /**
+     * @return {Promise<{y: number}>}
+     */
+    async didScrollToEnd() {
+        const { page } = this;
+        return await test.step(`manually setting scroll position to end of element`, async () => {
+            const y = await page.evaluate(() => {
+                const scroller = document.querySelector('[data-main-scroller]');
+                if (!scroller) throw new Error('missing element');
+                scroller.scrollTop = scroller.scrollHeight - scroller.clientHeight;
+                return scroller.scrollTop;
+            });
+            expect(y).toBeGreaterThan(0);
+            return { y };
+        });
+    }
+
+    /**
+     * @param {object} props
+     * @param {number} props.y
+     * @returns {Promise<void>}
+     */
+    async scrollIs({ y }) {
+        const { page } = this;
+        await test.step(`fetching the scroll position and comparing to ${y}`, async () => {
+            await page.waitForFunction(
+                ({ y }) => (document.querySelector('[data-main-scroller]')?.scrollTop ?? 0) === y,
+                { y },
+                { timeout: 1000 },
+            );
+        });
+    }
 }
 
 /**

special-pages/pages/new-tab/integration-tests/new-tab.spec.js

@@ -149,4 +149,27 @@ test.describe('newtab widgets', () => {
             await ntp.hasBackgroundColor({ hex: '#000000' });
         });
     });
+
+    test.describe('scroll restoration', () => {
+        test.use({ viewport: { height: 400, width: 800 } });
+        test('restores to previous position', async ({ page }, workerInfo) => {
+            const ntp = NewtabPage.create(page, workerInfo);
+            await ntp.reducedMotion();
+            await ntp.openPage({ additional: { tabs: true, 'tabs.debug': true } });
+
+            // initial
+            await ntp.scrollIs({ y: 0 });
+
+            // scroll to end
+            const tab1 = await ntp.didScrollToEnd();
+
+            // new tab = should be back to 0 for scroll
+            await ntp.didSwitchToTab('02', ['01', '02']);
+            await ntp.scrollIs({ y: 0 });
+
+            // now back to original
+            await ntp.didSwitchToTab('01', ['01', '02']);
+            await ntp.scrollIs({ y: tab1.y });
+        });
+    });
 });