Function setupIntersectionMocking

src/test-utils.ts:113–146

(mockFn: typeof vi.fn)

 * @param mockFn The mock function to use. Defaults to `vi.fn`.
 */
export function setupIntersectionMocking(mockFn: typeof vi.fn) {
  window.IntersectionObserver = mockFn(function IntersectionObserverMock(
    this: IntersectionObserver,
    cb,
    options = {},
  ) {
    const item = {
      callback: cb,
      elements: new Set<Element>(),
      created: Date.now(),
    };
    const instance: IntersectionObserver = {
      thresholds: Array.isArray(options.threshold)
        ? options.threshold
        : [options.threshold ?? 0],
      root: options.root ?? null,
      rootMargin: options.rootMargin ?? "",
      observe: mockFn((element: Element) => {
        item.elements.add(element);
      }),
      unobserve: mockFn((element: Element) => {
        item.elements.delete(element);
      }),
      disconnect: mockFn(() => {
        observers.delete(instance);
      }),
      takeRecords: mockFn(),
    };

    observers.set(instance, item);

    return instance;
  });
}

/**
 * Reset the IntersectionObserver mock to its initial state, and clear all the elements being observed.