如何在NodeJS中模拟流 [英] How to mock streams in NodeJS

问题描述

我正在尝试对大量处理流的node-js模块之一进行单元测试.我正在尝试模拟流(我将要写入的流)，因为在我的模块中，我想触发".on('data/end)"侦听器.本质上，我希望能够执行以下操作:

var mockedStream = new require('stream').readable();

mockedStream.on('data', function withData('data') {
  console.dir(data);
});

mockedStream.on('end', function() { 
  console.dir('goodbye');
});

mockedStream.push('hello world');
mockedStream.close();

这会执行，但是我执行推送后就不会触发"on"事件(并且.close()无效).

我在流上可以找到的所有指南都使用"fs"或"net"库作为创建新流的基础( https://github.com/substack/stream-handbook )，或者他们使用sinon对其进行了模拟，但模拟过程非常漫长，非常迅速.

有没有提供这样的虚拟流的好方法?

解决方案

我应该使用".emit(< event> ;,< data>);"而不是使用Push.

我的模拟代码现在可以正常工作，并且看起来像:

var mockedStream = new require('stream').Readable();
mockedStream._read = function(size) { /* do nothing */ };

myModule.functionIWantToTest(mockedStream); // has .on() listeners in it

mockedStream.emit('data', 'Hello data!');
mockedStream.emit('end');

I'm attempting to unit test one of my node-js modules which deals heavily in streams. I'm trying to mock a stream (that I will write to), as within my module I have ".on('data/end)" listeners that I would like to trigger. Essentially I want to be able to do something like this:

var mockedStream = new require('stream').readable();

mockedStream.on('data', function withData('data') {
  console.dir(data);
});

mockedStream.on('end', function() { 
  console.dir('goodbye');
});

mockedStream.push('hello world');
mockedStream.close();

This executes, but the 'on' event never gets fired after I do the push (and .close() is invalid).

All the guidance I can find on streams uses the 'fs' or 'net' library as a basis for creating a new stream (https://github.com/substack/stream-handbook), or they mock it out with sinon but the mocking gets very lengthy very quicky.

Is there a nice way to provide a dummy stream like this?

解决方案

Instead of using Push, I should have been using ".emit(<event>, <data>);"

My mock code now works and looks like:

var mockedStream = new require('stream').Readable();
mockedStream._read = function(size) { /* do nothing */ };

myModule.functionIWantToTest(mockedStream); // has .on() listeners in it

mockedStream.emit('data', 'Hello data!');
mockedStream.emit('end');

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