我尝试按照Jest文档中的ES6 Class Mocks页面来测试TypeScript类Consumer上的方法。这个类示例化一个Provider对象并调用它的方法，所以我想模拟Provider类。
目录结构：

.
├── __tests__
│   └── consumers
│       └── Consumer.test.ts
└── js
    ├── providers
    │   └── provider.ts
    └── consumers
        └── Consumer.ts

provider.ts：

export class Provider {
    constructor() {}

    public action(params) {
        // do some stuff that we need to mock
        return something;
    }
}

Consumer.ts：

import {Provider} from "../providers/provider";

export class Consumer {
    private provider: Provider;

    constructor() {
        this.provider = new Provider();
    }

    public doSomething() {
        const result = this.provider.action(params);
        // do something with 'result'
    }
}

我的第一次尝试是使用默认的“自动模拟”：
Consumer.test.ts：

import {Consumer} from "../../js/consumers/Consumer";

jest.mock("../../js/providers/provider");

test("Consumer doSomething", () => {
    // a mock Provider will be instantiated in Consumer's ctor:
    const consumer = new Consumer();

    // however, Provider.action() will return undefined within doSomething()
    consumer.doSomething();
});

这证明了我可以用mock替换真实的实现，但是我需要确保Provider.action()返回一个值，所以接下来我尝试了：

// at some point we can make this return something, but first check it works
const mockAction = jest.fn();
jest.mock("../../js/providers/provider", () => {
  return jest.fn().mockImplementation(() => {
    return {action: mockAction};
  });
});

test("Consumer doSomething", () => {
    // throws TypeError: provider_1.Provider is not a constructor
    const consumer = new Consumer();

    consumer.doSomething();
});

无论我如何尝试更改模拟，我都无法找到一个解决方案，使我可以在测试中正常使用Consumer。我宁愿避免创建“手动模拟”，这样我就可以保持代码库更干净，并在测试之间改变模拟实现。