如何重构调用函数的函数，使其可以使用 typescript 和 sinon 进行测试？

Question

我有以下代码

import {
    getIndexDocument
} from "@assets";

class MetaController {
     
    public async exploreIndexDocument(): Promise<Asset | undefined> {
         const {
            result: { assignedDirectories }
         } = await getIndexDocument(this._serviceConfig).catch(err => {
             throw new Error(`[AssetsController] Bad response on discovering index doc because ${err}`);
        });
     }
}

如您所见，exploreIndexDocument 正在调用函数 getIndexDocument。我想为 exploreIndexDocument 编写一个测试，但我不能使用 sinon 存根 getIndexDocument，因为 sinon 不允许您存根函数。我该如何构建这个 class 才能做到这一点？

Answer 1

您需要某种方式来注入存根，以便您的 class 实例调用它而不是外部库。 This answer elaborates some alternatives. The alternative to injecting stubs is to replace the entire module you are importing. This is called using a link seam. 并列出了各种可帮助您这样做的模块加载器。

就我个人而言，我已经慢慢摆脱了模块模拟技术，并试图让自己处于依赖注入的领域（备选方案 1），因为无论底层环境如何，它都可以工作，而且任何新手程序员都可以阅读测试。侵入性最小的方法可以简单地是这样的：

import {
    getIndexDocument
} from "@assets";

class MetaController {
    private getIndexDocument: (config:object) => Promise<{assignedDirectories:any> };

    constructor(deps = {getIndexDocument}) {
        this.getIndexDocument = getIndexDocument;
    }
     
    public async exploreIndexDocument(): Promise<Asset | undefined> {
        const {
            result: { assignedDirectories }
        } = await this.getIndexDocument(this._serviceConfig).catch(err => {
            throw new Error(`[AssetsController] Bad response on discovering index doc because ${err}`);
        });
     }
}

您现在可以非常轻松地进行测试：

const fake = sinon.fake.resolves({ assignedDirectories: ['/foo/dir'] });
const controller = new MetaController({getIndexDocument: fake});
const promise = controller.exploreIndexDocument();

expect(fake.calledOnce).toBe(true);
// further assertions follow ... see https://sinonjs.org/releases/latest/fakes/

如何重构调用函数的函数，使其可以使用 typescript 和 sinon 进行测试？

How to refactor a function that calls a function so that it can be tested using typescript and sinon?

sinon

typescript