When mocking a class in typescript using jest/ts-jest I am getting "TypeError: "X".default is not a constructor."

Question

我正在使用 typescript 中的 jest/ts-jest 编写单元测试，我正在尝试模拟 class 但我遇到了 TypeError。 "storage_1.default is not a constructor"。

这是我如何嘲笑 class。

index.test.ts

import GetAdaptiveCard from '../../GetAdaptiveCard/index'

const mockGetAdaptiveCard = jest.fn();
jest.mock('../../utils/storage', () => {
    return jest.fn().mockImplementation(() => {
        return {
            getAdaptiveCard: mockGetAdaptiveCard
        }   
    })
})
test('http trigger should return adaptive card', async () => {
....
    await GetAdaptiveCard(context, req);//calls AdaptiveCardStorage. The class I am mocking in "../../utils/storage"
...
});

index.ts

import AdaptiveCardsStorage from '../utils/storage';
...
const storage: AdaptiveCardsStorage = new AdaptiveCardsStorage(); //This is where I get the TypeError
const adaptiveCard: string = await storage.getAdaptiveCard(userID, cardName);

utils/storage.ts

export default class AdaptiveCardsStorage {
    /**
     * 
     * Class to interface with adaptive cards storage.
     * 
     */

    private tableService: storage.TableService;
    private tableName: string = Config["TABLE_STORAGE_TABLE_NAME"];

    public constructor() {
        this.tableService = storage.createTableService();
    }

    public async getAdaptiveCard(userID: string, cardName: string): Promise<string> {
        return new Promise((resolve, reject) => {
            this.tableService.retrieveEntity<any>(this.tableName, userID, cardName, (err, result) => {
                if (!err) {
                    resolve(result.Content["_"]);
                } else {
                    reject(err);
                }
            });
        });
    }

}

这就是我得到的。

    TypeError: storage_1.default is not a constructor


const handleRequest = async function (userID: string, cardName: string, context: Context) {
const storage: AdaptiveCardsStorage = new AdaptiveCardsStorage();
         |                                           ^
const adaptiveCard: string = await storage.getAdaptiveCard(userID, cardName);

at GetAdaptiveCard/index.ts:19:
at dist/GetAdaptiveCard/index.js:7:71
at Object.<anonymous>.__awaiter (dist/GetAdaptiveCard/index.js:3:12)
at handleRequest (dist/GetAdaptiveCard/index.js:29:
at Object.<anonymous> (GetAdaptiveCard/index.ts:9:29)
at dist/GetAdaptiveCard/index.js:7:71

Answer 1

因为您的代码使用的是 ES2015 imports，所以它期望您的模块的 default 导出可用，但在模拟中您没有提供。修复非常简单：

jest.mock('../../utils/storage', () => {
    return { // need to add this nested `default` property
        default: jest.fn().mockImplementation(() => {
            return {
                getAdaptiveCard: mockGetAdaptiveCard
            }   
        })
    }
})

Answer 2

作为对 Dmitriy 的回应，请记住，如果您以 export class AdaptiveCardsStorage 的方式导出 class，您将在模拟中反映该命名空间。

jest.mock('../../utils/storage', () => {
    return { // need to add this nested `default` property
        AdaptiveCardsStorage: jest.fn().mockImplementation(() => {
            return {
                getAdaptiveCard: mockGetAdaptiveCard
            }   
        })
    }
})

When mocking a class in typescript using jest/ts-jest I am getting "TypeError: "X".default is not a constructor."

When mocking a class in typescript using jest/ts-jest I am getting "TypeError: "X".default is not a constructor."

mocking

typescript

jestjs

ts-jest