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import { noop } from 'lodash';
import { TEST_HOST } from 'helpers/test_constants';
import { useMockMutationObserver, useMockIntersectionObserver } from 'helpers/mock_dom_observer';
import LazyLoader from '~/lazy_loader';
import waitForPromises from './helpers/wait_for_promises';
const execImmediately = callback => {
callback();
};
const TEST_PATH = `${TEST_HOST}/img/testimg.png`;
describe('LazyLoader', () => {
let lazyLoader = null;
const { trigger: triggerMutation } = useMockMutationObserver();
const { trigger: triggerIntersection } = useMockIntersectionObserver();
const triggerChildMutation = () => {
triggerMutation(document.body, { options: { childList: true, subtree: true } });
};
const triggerIntersectionWithRatio = img => {
triggerIntersection(img, { entry: { intersectionRatio: 0.1 } });
};
const createLazyLoadImage = () => {
const newImg = document.createElement('img');
newImg.className = 'lazy';
newImg.setAttribute('data-src', TEST_PATH);
document.body.appendChild(newImg);
triggerChildMutation();
return newImg;
};
const createImage = () => {
const newImg = document.createElement('img');
newImg.setAttribute('src', TEST_PATH);
document.body.appendChild(newImg);
triggerChildMutation();
return newImg;
};
const mockLoadEvent = () => {
const addEventListener = window.addEventListener.bind(window);
jest.spyOn(window, 'addEventListener').mockImplementation((event, callback) => {
if (event === 'load') {
callback();
} else {
addEventListener(event, callback);
}
});
};
beforeEach(() => {
jest.spyOn(window, 'requestAnimationFrame').mockImplementation(execImmediately);
jest.spyOn(window, 'requestIdleCallback').mockImplementation(execImmediately);
jest.spyOn(LazyLoader, 'loadImage');
mockLoadEvent();
});
afterEach(() => {
document.body.innerHTML = '';
});
describe.each`
hasIntersectionObserver | trigger
${true} | ${triggerIntersectionWithRatio}
${false} | ${noop}
`(
'with hasIntersectionObserver=$hasIntersectionObserver',
({ hasIntersectionObserver, trigger }) => {
let origIntersectionObserver;
beforeEach(() => {
origIntersectionObserver = global.IntersectionObserver;
global.IntersectionObserver = hasIntersectionObserver
? global.IntersectionObserver
: undefined;
lazyLoader = new LazyLoader({
observerNode: 'foobar',
});
});
afterEach(() => {
global.IntersectionObserver = origIntersectionObserver;
lazyLoader.unregister();
});
it('determines intersection observer support', () => {
expect(LazyLoader.supportsIntersectionObserver()).toBe(hasIntersectionObserver);
});
it('should copy value from data-src to src for img 1', () => {
const img = createLazyLoadImage();
// Doing everything that happens normally in onload
lazyLoader.register();
trigger(img);
expect(LazyLoader.loadImage).toHaveBeenCalledWith(img);
expect(img.getAttribute('src')).toBe(TEST_PATH);
expect(img.getAttribute('data-src')).toBe(null);
expect(img).toHaveClass('js-lazy-loaded');
});
it('should lazy load dynamically added data-src images', async () => {
lazyLoader.register();
const newImg = createLazyLoadImage();
trigger(newImg);
await waitForPromises();
expect(LazyLoader.loadImage).toHaveBeenCalledWith(newImg);
expect(newImg.getAttribute('src')).toBe(TEST_PATH);
expect(newImg).toHaveClass('js-lazy-loaded');
});
it('should not alter normal images', () => {
const newImg = createImage();
lazyLoader.register();
expect(LazyLoader.loadImage).not.toHaveBeenCalled();
expect(newImg).not.toHaveClass('js-lazy-loaded');
});
it('should not load dynamically added pictures if content observer is turned off', async () => {
lazyLoader.register();
lazyLoader.stopContentObserver();
const newImg = createLazyLoadImage();
await waitForPromises();
expect(LazyLoader.loadImage).not.toHaveBeenCalledWith(newImg);
expect(newImg).not.toHaveClass('js-lazy-loaded');
});
it('should load dynamically added pictures if content observer is turned off and on again', async () => {
lazyLoader.register();
lazyLoader.stopContentObserver();
lazyLoader.startContentObserver();
const newImg = createLazyLoadImage();
trigger(newImg);
await waitForPromises();
expect(LazyLoader.loadImage).toHaveBeenCalledWith(newImg);
expect(newImg.getAttribute('src')).toBe(TEST_PATH);
expect(newImg).toHaveClass('js-lazy-loaded');
});
},
);
});
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