reactjs - 如何使用 react 测试库模拟 ResizeObserver 以在单元测试中工作

Question

如果有人可以提供帮助，我有一个自定义钩子(Hook)，它使用 ResizeObserver 来更改组件的宽度。我的问题是，当我去运行我的单元测试时，它会破坏我所有的测试并且查看快照它并没有渲染 dom 中的所有元素。在我实现 ResizeObserver 之前它一直在工作。有谁知道我是否有办法将 ResizeObserver 模拟为未定义。或者其他建议。

import * as React from 'react';
import ResizeObserver from 'resize-observer-polyfill';

const useResizeObserver = (ref: { current: any }) => {
    const [dimensions, setDimensions] = React.useState<DOMRectReadOnly>();
    React.useEffect(() => {
        const observeTarget = ref.current;
        const resizeObserver = new ResizeObserver((entries) => {
            entries.forEach((entry) => {
                setDimensions(entry.contentRect);
            });
        });
        resizeObserver.observe(observeTarget);
        return () => {
            resizeObserver.unobserve(observeTarget);
        };
    }, [ref]);
    return dimensions;
};

export default useResizeObserver;



import { render, screen, waitFor } from '@testing-library/react';
import userEvent from '@testing-library/user-event';
import React from 'react';

import mockFetchProfileActivity from '../../../services/mocks/fetch-profile-activity';
import BarChart from './BarChart';

const component = <BarChart userActivity={mockFetchProfileActivity} />;

describe('Render barElement Chart component', () => {
    const observers: any[] = [];
    let resizeHandler: (observers: any[]) => void;
    (window as any).ResizeObserver = (e: any) => {
        resizeHandler = e;

        return {
            observe(element: any) {
                observers.push(element);
            },
            unobserve(element: any) {
                const i = observers.indexOf(element);
                if (i !== -1) {
                    observers.splice(i, 1);
                }
            }
        };
    };

    it('Matches the snapshot', () => {
        // resizeHandler(observers);
        const container = render(component);
        expect(container).toMatchSnapshot();
    });

    it('when clicking on a chart barElement drilldown "challenges" are shown', async () => {
        // arrange
        const componentRender = render(component);
        waitFor(() => resizeHandler(observers));

        // act
        const barElement = componentRender.container.querySelector('svg rect');

        if (barElement) userEvent.click(barElement);

        // assert
        expect(screen.getByText('Challenge 1')).toBeInTheDocument();
    });
});

Answer 1

我选择将 polyfill 添加为开发依赖项，并将以下行添加到 setupTests.js/ts:

global.ResizeObserver = require('resize-observer-polyfill')