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1.6 kB · 44 lines
TypeScript
at main
123456789101112131415161718192021222324252627282930313233343536373839404142434445import {createRowObserver} from './createRowObserver'
test('shares observation, routes entries, and releases the last observer', () => { const original = globalThis.IntersectionObserver let deliver!: IntersectionObserverCallback const observe = jest.fn() const unobserve = jest.fn() const disconnect = jest.fn() const construct = jest.fn(callback => { deliver = callback return {observe, unobserve, disconnect} }) globalThis.IntersectionObserver = construct as unknown as typeof IntersectionObserver try { const subscribe = createRowObserver({rootMargin: '800px'}) const first = {} as Element const second = {} as Element const firstCallback = jest.fn() const secondCallback = jest.fn() const releaseFirst = subscribe(first, firstCallback) const releaseSecond = subscribe(second, secondCallback) expect(construct).toHaveBeenCalledTimes(1) const entry = { target: second, isIntersecting: true, } as IntersectionObserverEntry deliver([entry], {} as IntersectionObserver) expect(firstCallback).not.toHaveBeenCalled() expect(secondCallback).toHaveBeenCalledWith([entry]) releaseFirst() expect(unobserve).toHaveBeenCalledWith(first) expect(disconnect).not.toHaveBeenCalled() deliver([{...entry, target: first}], {} as IntersectionObserver) expect(firstCallback).not.toHaveBeenCalled() releaseSecond() expect(disconnect).toHaveBeenCalledTimes(1) const releaseNew = subscribe(first, firstCallback) expect(construct).toHaveBeenCalledTimes(2) releaseNew() } finally { globalThis.IntersectionObserver = original }})