如何为express.static模拟http.ServerResponse和http.IncomingMessage

Question

我测试自己的路由处理程序没有问题,但在这种情况下我想测试express的静态处理程序.我无法为我的生活弄清楚为什么它会悬挂.显然,我缺少一些回调或者我需要发出一些事件.

我尽力做出最小的例子.

var events = require('events');
var express = require('express');
var stream = require('stream');
var util = require('util');

function MockResponse(callback) {
  stream.Writable.call(this);
  this.headers = {};
  this.statusCode = -1;
  this.body = undefined;

  this.setHeader = function(key, value) {
    this.headers[key] = value;
  }.bind(this);

  this.on('finish', function() {
    console.log("finished response");
    callback();
  });
};

util.inherits(MockResponse, stream.Writable);

MockResponse.prototype._write = function(chunk, encoding, done) {
  if (this.body === undefined) {
    this.body = "";
  }
  this.body += chunk.toString(encoding !== 'buffer' ? encoding : undefined);
  done();
};

function createRequest(req) {
  var emitter = new events.EventEmitter();
  req.on = emitter.on.bind(emitter);
  req.once = emitter.once.bind(emitter);
  req.addListener = emitter.addListener.bind(emitter);
  req.emit = emitter.emit.bind(emitter);
  return req;
};

describe('test', function() {

  var app;

  before(function() {
    app = express();
    app.use(express.static(__dirname));
  });

  it('gets test.js', function(done) {

    var req = createRequest({
        url: "http://foo.com/test.js",
        method: 'GET',
        headers: {
        },
    });
    var res = new MockResponse(responseDone);
    app(req, res);

    function responseDone() {
      console.log("done");
      done();
    }

  });

});

建立,

mkdir foo
cd foo
mkdir test
cat > test/test.js   # copy and paste code above
^D
npm install express
npm install mocha
node node_modules/mocha/bin/mocha --recursive

它只是超时了.

我错过了什么？

我也尝试将请求设为可读流.没变

var events = require('events');
var express = require('express');
var stream = require('stream');
var util = require('util');

function MockResponse(callback) {
  stream.Writable.call(this);
  this.headers = {};
  this.statusCode = -1;
  this.body = undefined;

  this.setHeader = function(key, value) {
    this.headers[key] = value;
  }.bind(this);

  this.on('finish', function() {
    console.log("finished response");
    callback();
  });
};

util.inherits(MockResponse, stream.Writable);

MockResponse.prototype._write = function(chunk, encoding, done) {
  if (this.body === undefined) {
    this.body = "";
  }
  this.body += chunk.toString(encoding !== 'buffer' ? encoding : undefined);
  done();
};

function MockMessage(req) {
  stream.Readable.call(this);
  var self = this;
  Object.keys(req).forEach(function(key) {
    self[key] = req[key];
  });
}

util.inherits(MockMessage, stream.Readable);

MockMessage.prototype._read = function() {
  this.push(null);
};


describe('test', function() {

  var app;

  before(function() {
    app = express();
    app.use(express.static(__dirname));
  });

  it('gets test.js', function(done) {

    var req = new MockMessage({
        url: "http://foo.com/test.js",
        method: 'GET',
        headers: {
        },
    });
    var res = new MockResponse(responseDone);
    app(req, res);

    function responseDone() {
      console.log("done");
      done();
    }

  });

});

我一直在挖掘.查看静态服务器内部我看到它通过调用创建了一个可读流fs.createReadStream.它确实有效

var s = fs.createReadStream(filename);
s.pipe(res);

所以试着让自己工作得很好

  it('test stream', function(done) {
    var s = fs.createReadStream(__dirname + "/test.js");
    var res = new MockResponse(responseDone);
    s.pipe(res);

    function responseDone() {
      console.log("done");
      done();
    }    
  });

我想也许这是关于表达等待输入流完成的东西,但这似乎也不是.如果我使用响应使用模拟输入流,它就可以正常工作

  it('test msg->res', function(done) {
    var req = new MockMessage({});
    var res = new MockResponse(responseDone);
    req.pipe(res);

    function responseDone() {
      console.log("done");
      done();
    }    
  });

任何有关我可能缺少的东西都会有所帮助

注意:虽然对第三方模拟库的建议表示赞赏但我仍然真的希望了解我自己缺少的东西.即使我最终切换到某个库,我仍然想知道为什么这不起作用.

Answer 1

我发现了两个阻止finish回调执行的问题.

1. serve-static使用send模块,该模块用于从路径创建文件读取流并将其传递给res对象.但该模块使用on-finished模块检查finished响应对象中是否将属性设置为false,否则会破坏文件读取流.因此,文件流永远不会有机会发出数据事件.

2. 快递初始化覆盖响应对象的原型.因此end(),http响应原型会覆盖像方法这样的默认流方法:

   exports.init = function(app){
     return function expressInit(req, res, next){
       ...
       res.__proto__ = app.response;
       ..
     };
   };
   

   为了防止这种情况,我在静态中间件之前添加了另一个中间件,将其重置为MockResponse原型:

   app.use(function(req, res, next){
     res.__proto__ = MockResponse.prototype; //change it back to MockResponse prototype
     next();
   });
   

以下是为使其适用的更改MockResponse:

...
function MockResponse(callback) {
  ...
  this.finished = false; // so `on-finished` module doesn't emit finish event prematurely

  //required because of 'send' module
  this.getHeader = function(key) {
    return this.headers[key];
  }.bind(this);
  ...
};

...
describe('test', function() {

  var app;

  before(function() {
    app = express();

    //another middleware to reset the res object
    app.use(function(req, res, next){
      res.__proto__ = MockResponse.prototype;
      next();
    });

    app.use(express.static(__dirname));
  });

  ...

});

编辑:

正如@gman指出的那样,可以使用直接属性而不是原型方法.在这种情况下,不需要覆盖原型的额外中间件:

function MockResponse(callback) {
  ...
  this.finished = false; // so `on-finished` module doesn't emit finish event prematurely

  //required because of 'send' module
  this.getHeader = function(key) {
     return this.headers[key];
  }.bind(this);

  ...

  //using direct property for _write, write, end - since all these are changed when prototype is changed
  this._write = function(chunk, encoding, done) {
    if (this.body === undefined) {
      this.body = "";
    }
    this.body += chunk.toString(encoding !== 'buffer' ? encoding : undefined);
    done();
  };

  this.write = stream.Writable.prototype.write;
  this.end = stream.Writable.prototype.end;

};