Question

我正在构建一个将包装SignalR库的客户端：

export class RealTimeCommunicator {

  /** SignalR hub connection */
  private hubConnection: HubConnection | null = null;

  private buildConnection(url: string): HubConnection {
    return new HubConnectionBuilder()
    .withUrl(url)
    .build();
  }

  public subscribe(onStart: () => void, success: (data: IVehicleInfo) => void, fail?: (err: Error) => void): () => void {
    this.hubConnection = this.buildConnection("/someurl");
    this.hubConnection.on("send", data => {
      success(data);
    });

    this.hubConnection.start()
      .then(onStart)
      .catch(err => fail && fail(err));

    return this.unsubscribe;
  }

  public subscribeToVehicleDetails(vehicleId: number, success: (data: IVehicleInfo) => void, fail?: (err: Error) => void): () => void {
    return this.subscribe(() => this.hubConnection!.invoke("EnrolInVehicleGroupAsync", vehicleId), success, fail);
  }

我想测试它，但是模拟SignalR，所以我在解决方案中添加了__mocks__/@aspnet/signalr.ts：

let SignalR = jest.genMockFromModule("@aspnet/signalr");

class HubConnection {

  public on(methodName: string, callback: () => string): Promise<void> {
    this.successCallback = callback;
    return Promise.resolve()
  }

  public start(): Promise<void> { return Promise.resolve() }

  public successCallback: () => string = () => "failure";
}

let hubConnection = new HubConnection();

let HubConnectionBuilder = () => ({
  withUrl: (url) => ({
    build: () => hubConnection
  })
});

SignalR = {
  HubConnectionBuilder: HubConnectionBuilder,
  HubConnection: hubConnection
};

module.exports = SignalR;

我正在尝试监视on方法以确保已被调用，并作为扩展目标确认我的成功处理程序已正确注册。

import { RealTimeCommunicator } from "./RealTimeCommunicator";
jest.mock('SignalR');

describe("RTC", () => {
  test("foo", () => {
    const ConnectionBuilder = require("SignalR").HubConnectionBuilder;

    const connection = new ConnectionBuilder().withUrl("").build();

    const spy = jest.spyOn(connection, 'on');
    expect(spy).toHaveBeenCalled();  //Expectation fails
    const successText = "success!";
    const successCallBack: () => string = () => successText;
    const rtc = new RealTimeCommunicator();

    rtc.subscribeToVehicleDetails(1, successCallBack, _ => _);
    expect(connection.successCallback()).toBe(successText); // connection.successCallback is undefined
  })
});

如果我在SignalR模拟中放置断点，则可以看到on正在被调用，但间谍却看不到它。同样，我在模拟游戏上狂奔的successCallback又回到了undefined

Answer 1

您能提供任何可行的示例（例如以回购形式）重现您的问题吗？据我所知，所提供的代码段中存在一些缺陷。

首先，jest.mock('SignalR');为何真正起作用？ SignalR 不是应该抛出错误的模块。您应该模拟实际要导入的模块：jest.mock('@aspnet/signalr');。除此之外，测试的第一部分包括测试第三方库-除了检查您的模拟程序是否正常工作之外，您为什么要这样做？

第二，您要检查创建间谍后on方法是否被立即调用。但是，间谍只记录创建后的调用。您可能想要的是默认情况下使 on 方法成为间谍：

// in __mocks__/@aspnet/signalr.ts

class HubConnection {

  public on = jest.fn().mockImplementation((methodName: string, callback: () => string) => {
    this.successCallback = callback;
    return Promise.resolve()
  });


  // ...

}

第三，您在测试中创建的连接与以后使用 subscribeToVehicleDetails 创建的连接不同，因此successCallback仍将返回“失败”如果可以的话。

Answer 2

您已经接近，只需要进行两项更改即可。

返回success(data)的结果：

public subscribe(onStart: () => void, success: (data: IVehicleInfo) => void, fail?: (err: Error) => void): () => void {
  this.hubConnection = this.buildConnection("/someurl");
  this.hubConnection.on("send", data => {
    return success(data);   // return the result
  });

  this.hubConnection.start()
    .then(onStart)
    .catch(err => fail && fail(err));

  return this.unsubscribe;
}

等待断言spy已被调用，直到之后您致电rtc.subscribeToVehicleDetails：

const spy = jest.spyOn(connection, 'on');
const successText = "success!";
const successCallBack: () => string = () => successText;
const rtc = new RealTimeCommunicator();

rtc.subscribeToVehicleDetails(1, successCallBack, _ => _);
expect(spy).toHaveBeenCalled();   // SUCCESS
expect(connection.successCallback()).toBe(successText);   // SUCCESS

监视传递到模拟节点模块中的方法

2 个答案: