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import { beforeEach, describe, expect, it, jest } from '@jest/globals';
import { renderHook } from '@testing-library/react';
import { useMutationObserver } from './use-mutation-observer';
describe('useMutationObserver', () => {
beforeEach(() => {
jest.restoreAllMocks();
});
it('can create a new observer', () => {
const callback = jest.fn();
const observerSpy = jest.spyOn(MutationObserver.prototype, 'observe');
const wrapper = document.createElement('div');
const options: MutationObserverInit = { childList: true };
renderHook(() =>
useMutationObserver({
callback,
options,
ref: { current: wrapper },
})
);
expect(observerSpy).toHaveBeenCalledTimes(1);
expect(observerSpy).toHaveBeenCalledWith(wrapper, options);
});
it('does not create a new observer when ref is null', () => {
const callback = jest.fn();
const observerSpy = jest.spyOn(MutationObserver.prototype, 'observe');
renderHook(() =>
useMutationObserver({
callback,
options: { childList: true },
ref: { current: null },
})
);
expect(observerSpy).not.toHaveBeenCalled();
});
});
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