我尝试测试 onmessage 是否是一个正确的函数。

这是一个测试:

  describe(".init(address, window)", function() {
    beforeEach(function() {
      address = 'ws://test.address';
      window = {};
      e = {
        data: {}
      }
      spyOn(window, 'WebSocket').and.returnValue(function() {return {onmessage: null}});
      spyOn(subject, 'handleMessage');
    });

    it("should create a WebSocket client which connects to the given address", function() {
      subject.init(address, window);
      expect(window.WebSocket).toHaveBeenCalledWith(address);
    });

    it("should have onmessage method overriden with a function which handles message", function() {
      ws = subject.init(address, window);
      alert(JSON.stringify(ws));
      ws.onmessage(e);
      expect(subject.handleMessage).toHaveBeenCalledWith(e.data);
    });
  });

这里是实现:

FL.init = function(address, window) {
  if ('WebSocket' in window) {
    var ws = new WebSocket(address);
    ws.onmessage = function(e) {
      this.handleMessage(e.data);
    };
    return ws;
  }
};

第一个测试通过。在第二个中，ws 是 undefined。这是为什么？我在控制台 new function() {return {onmessage: null}} 中尝试过，看起来应该没问题。

最佳答案

我不完全确定我是否弄清楚了您的代码应该如何运行，但是如果您需要监视 WebSocket 构造函数和 stub .send 方法以模拟一些传入的消息，这里是实现它的方法。

要监视 WebSocket，您需要调用 .and.callThrough 而不是 returnValue。然而，它会导致提示缺少 new 关键字(如 here 中所述)，因此您需要伪造构造函数:

var realWS = WebSocket;
var WebSocketSpy = spyOn(window, "WebSocket").and.callFake(function(url,protocols){
  return new realWS(url,protocols);
});

要为收到的消息制作一个 spy ，你可以简单地做

var onmessageCallbackSpy = jasmine.createSpy('onmessageCallback');

您还可以监视 .send 方法，并提供一些模拟响应:

var sendSpy = spyOn(WebSocket.prototype, "send").and.callFake(function(outMsg){
  // process/check outgoing message
  // setTimeout, or call it immediately
  this.onmessage("mock message goes here");
}); 

但在用 WebSocketSpy 替换它之前，请确保使用 WebSocket.prototype。

如此完整的工作示例，应该如下所示:

it("should spy and callFake WebSocket constructor, and stub prototype methods", function (done) {
    var realWS= WebSocket;  
    var sendSpy = spyOn(WebSocket.prototype, "send").and.callFake(function(outMsg){
      if(outMsg == "outgoing message"){
        this.onmessage("incoming mocked message goes here");
      }
    });  
    // var messageSpy = spyOn(WebSocket.prototype, "onmessage");//.and.returnValue("mock message goes here");      
    var WSSpy = spyOn(window, "WebSocket").and.callFake(function(url,protocols){
      return new realWS(url,protocols);
    }); 
    var onmessageCallbackSpy = jasmine.createSpy('onmessageCallback');       

    // Your code
    // (function init(url, onmessageCallbackSpy){
        var ws = new WebSocket("ws://some/where");
        ws.onmessage = onmessageCallbackSpy;
        // code that results with receiving a message
        // or mocked send, that calls `.onmessage` immediately
        ws.send("outgoing message");
    // })();    

    expect(WSSpy).toHaveBeenCalledWith("ws://some/where");
    expect(onmessageCallbackSpy).toHaveBeenCalledWith("mock message goes here");
    done();
});

关于javascript - 使用 Jasmine 在 JavaScript 中插入 WebSocket，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/23151954/