Question

我在为模块运行Jest测试时遇到了麻烦-我有一个简单的入口点类：

import { Callback, CloudFrontRequestEvent, Context, Handler } from "aws-lambda";

import { CloudFrontHandler } from "./CloudFrontHandler";
import { OriginClient } from "./OriginClient";
import { ResponseRenderer } from "./ResponseRenderer";
import { TemplateRenderer } from "./TemplateRenderer";

export class LambdaHandler {
    private readonly renderer: TemplateRenderer;

    constructor(renderer: TemplateRenderer) {
        this.renderer = renderer;
    }

    public handle: Handler = (event: CloudFrontRequestEvent, _: Context, callback: Callback): void => {
        console.log(new CloudFrontHandler(null, null)); // <- just an empty object here! CloudFrontHandler {}
        console.log(new OriginClient(null)); // <- properly mocked
        console.log(new ResponseRenderer(null, null)); // <- properly mocked
        new CloudFrontHandler(
            new OriginClient(event.Records[0].cf.request),
            new ResponseRenderer(callback, this.renderer),
        )
            .handle(); // <- because CloudFrontHandler is not mocked, an error occurs here
    }
}

无论出于何种原因，CloudFrontHandler类都不会被嘲笑（OriginClient和ResponseRenderer会被自动模拟）。以下是我的测试课：

import "jest";
import { Callback, CloudFrontRequest, CloudFrontRequestEvent } from "aws-lambda";
import { mocked } from "ts-jest/utils";
import { LambdaHandler, TemplateRenderer } from "../../../main/nodejs";

import { CloudFrontHandler } from "../../../main/nodejs/edge/CloudFrontHandler";
import { OriginClient } from "../../../main/nodejs/edge/OriginClient";
import { ResponseRenderer } from "../../../main/nodejs/edge/ResponseRenderer";

jest.mock("../../../main/nodejs/edge/CloudFrontHandler");
jest.mock("../../../main/nodejs/edge/OriginClient");
jest.mock("../../../main/nodejs/edge/ResponseRenderer");

const MockedCloudFrontHandler = mocked(CloudFrontHandler);
const MockedOriginClient = mocked(OriginClient);
const MockedResponseRenderer = mocked(ResponseRenderer);

describe("LambdaHandler", (): void => {
        it("should handle CloudFront request", (): void => {
                const templateRenderer: TemplateRenderer = {} as TemplateRenderer;
                const callback: Callback = jest.fn() as Callback;
                const request: CloudFrontRequest = {} as CloudFrontRequest;
                const event: CloudFrontRequestEvent = {
                    Records: [
                        {
                            cf: {
                                request: request,
                            },
                        },
                    ],
                } as CloudFrontRequestEvent;

                let handler: LambdaHandler = new LambdaHandler(templateRenderer);
                handler.handle(event, null, callback)
                // todo

                expect(MockedCloudFrontHandler).toHaveBeenCalledTimes(1);
                expect(MockedOriginClient).toHaveBeenCalledTimes(1);
                expect(MockedResponseRenderer).toHaveBeenCalledTimes(1);
        });
});

（我将源文件和测试文件分开保存，因此所有这些src/main src/test路径）

为什么Jest不会嘲笑这一模块类？

-编辑-

错误消息是：

TypeError: (intermediate value).handle is not a function

Answer 1

我的问题下的注释使我找到了根本原因-这里的问题是CloudFrontHandler.handle是一个箭头函数，TypeScript将该箭头函数转换为构造函数中分配的属性。由于构造函数是自动模拟的，因此不会分配该函数。为.handle()方法创建手动模拟可以解决此问题。

笑话自动模拟不适用于模块

1 个答案: