多个 React-dnd 笑话测试“不能同时有两个 HTML5 后端”

Question

我有一个 jest 测试文件，其中包含许多测试。

import React from 'react';
import configureStore from 'redux-mock-store';
import {Provider} from "react-redux";
import renderer from "react-test-renderer";
import HTML5Backend from "react-dnd-html5-backend";
import {DragDropContextProvider} from "react-dnd";

describe('My Component Tests', () => {
    let mockStore;
    let store;

    beforeEach(() => {
        mockStore = configureStore();
        store = mockStore(mockData);
    });

    test(' test1', () => {
        const cmpt = <Provider store={store}>
            <DragDropContextProvider backend={HTML5Backend}>
                <MyComponent state={1}/>
            </DragDropContextProvider>
        </Provider>;

        const tree = renderer.create(cmpt).toJSON();
        expect(tree).toMatchSnapshot();
    });

    test(' test2', () => {
        const cmpt = <Provider store={store}>
            <DragDropContextProvider backend={HTML5Backend}>
                <MyComponent state={2}/>
            </DragDropContextProvider>
        </Provider>;

        const tree = renderer.create(cmpt).toJSON();
        expect(tree).toMatchSnapshot();
    });
});

第一次测试总是有效

但是后面的总是会出现这个错误：

 Error: Uncaught [Error: Cannot have two HTML5 backends at the same time.]

我猜这是因为 HTMLBackend 被视为单例，并且用于跨测试，这不是我想要的。我想要独立运行的测试。

有没有在 beforeEach() 函数中创建 HTMLBackend 的实例。

我试图将 HTML5Backend 封装成一个单例，但我遇到了同样的问题：

let html5Backend = null;

function getSingleton() {
    if (!html5Backend) {
        html5Backend = HTML5Backend;
        debugger;
    }
    return html5Backend;
}

Answer 1

我通过在“描述”级别引用 HTMLBackend 实例解决了这个问题，如下所示：

describe('My Component Tests', () => {
    let mockStore;
    let store;

    let htmlbe = HTML5Backend; //reference instance here!!!

    beforeEach(() => {
        mockStore = configureStore();
        store = mockStore(mockData);
    });

    test(' test1', () => {
        const cmpt = <Provider store={store}>
            <DragDropContextProvider backend={htmlbe }>
                <MyComponent state={1}/>
            </DragDropContextProvider>
        </Provider>;

        const tree = renderer.create(cmpt).toJSON();
        expect(tree).toMatchSnapshot();
    });

    test(' test2', () => {
        const cmpt = <Provider store={store}>
            <DragDropContextProvider backend={htmlbe }>
                <MyComponent state={2}/>
            </DragDropContextProvider>
        </Provider>;

        const tree = renderer.create(cmpt).toJSON();

这相当于在所有测试中都有一个单例。