Merge pull request #13679 from bbc/WS-2012-live-page-refresh-spike

[WS-2012] Initial Implementation of Live Page Refresh button (Frontend only)

Author: shayneahchoon

src/app/components/intersection-observer-testing-library.tsx

@@ -0,0 +1,43 @@
+export default class MockIntersectionObserver {
+  observers;
+
+  constructor() {
+    this.observers = new Map();
+  }
+
+  getMockIntersectionObserver = () => {
+    const mockIntersectionObserver = cb => {
+      const item = {
+        callback: cb,
+        elements: new Set(),
+      };
+
+      const instance = {
+        observe: jest.fn(element => {
+          item.elements.add(element);
+        }),
+        disconnect: jest.fn(() => {
+          item.elements.clear();
+        }),
+      };
+
+      this.observers.set(instance, item);
+
+      return instance;
+    };
+
+    return mockIntersectionObserver;
+  };
+
+  triggerAllObservers = () => {
+    this.observers.forEach(item => {
+      item.callback([
+        { isIntersecting: true, boundingClientRect: { bottom: 1 } },
+      ]);
+    });
+  };
+
+  clearObservers = () => {
+    this.observers.clear();
+  };
+}

src/app/hooks/useLivePagePolling/fakeRequest.ts

@@ -0,0 +1,6 @@
+import { ComponentProps } from '#nextjs/pages/[service]/live/[id]/LivePageLayout';
+
+// This is a placeholder function, this will be replaced by a proper fetch statement to the BFF in due time.
+export default () => {
+  return null as unknown as ComponentProps['pageData'];
+};