87 lines
2.3 KiB
JavaScript
87 lines
2.3 KiB
JavaScript
import { create } from '~/lib/utils/intersection_observer';
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describe('IntersectionObserver Utility', () => {
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beforeAll(() => {
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global.IntersectionObserver = class MockIntersectionObserver {
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constructor(callback) {
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this.callback = callback;
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this.entries = [];
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}
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addEntry(entry) {
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this.entries.push(entry);
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}
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trigger() {
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this.callback(this.entries);
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}
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};
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});
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describe('create', () => {
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describe('memoization', () => {
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const options = { rootMargin: '1px 1px 1px 1px' };
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let expectedOutput;
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beforeEach(() => {
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create.cache.clear();
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expectedOutput = create(options);
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});
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it('returns the same Observer for the same options input', () => {
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expect(expectedOutput.id).toBe(create(options).id);
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});
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it('creates a new Observer for unique input options', () => {
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expect(expectedOutput.id).not.toBe(create({ rootMargin: '1px 2px 3px 4px' }));
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});
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it('creates a new Observer for the same input options in different object references', () => {
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expect(expectedOutput.id).not.toBe(create({ rootMargin: '1px 1px 1px 1px' }));
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});
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});
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});
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describe('Observer behavior', () => {
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let observer = null;
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let id = null;
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beforeEach(() => {
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create.cache.clear();
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({ observer, id } = create());
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});
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it.each`
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isIntersecting | event
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${false} | ${'IntersectionDisappear'}
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${true} | ${'IntersectionAppear'}
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`(
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'should emit the correct event on the entry target based on the computed Intersection',
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async ({ isIntersecting, event }) => {
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const target = document.createElement('div');
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observer.addEntry({ target, isIntersecting });
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target.addEventListener(event, (e) => {
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expect(e.detail.observer).toBe(id);
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});
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observer.trigger();
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},
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);
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it('should always emit an Update event with the entry and the observer', () => {
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const target = document.createElement('div');
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const entry = { target };
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observer.addEntry(entry);
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target.addEventListener('IntersectionUpdate', (e) => {
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expect(e.detail.observer).toBe(id);
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expect(e.detail.entry).toStrictEqual(entry);
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});
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observer.trigger();
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});
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});
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});
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