如何在Node.js上使用Mocha进行单元测试控制台输出? [英] How to unit test console output with mocha on nodejs?

问题描述

请考虑以下以下示例Javascript代码:

Take into account the following example Javascript code below:

function privateFunction (time) {
  if (time < 12) { console.log('Good morning'); }
  if (time >= 12 && time <19) { console.log('Good afternoon'); }
  else { console.log('Good night!'); }
};

我应该如何使用mocha(可能还有sinonjs)在nodejs上进行单元测试，注意这是在模块内部调用的私有函数?我需要传递参数，并检查函数是否将正确的内容记录到控制台.

How should I unit test that on nodejs using mocha (and possibly sinonjs), noticing that this is a private function called inside a module? I need to pass in the argument and check if the function is logging the right thing to the console.

我可以对console.warn和console.error做同样的事情吗?

Can I do the same with console.warn and console.error?

推荐答案

与普通"相比，我更喜欢 mocha-sinon sinon，因为它与Mocha很好地集成了.

I prefer mocha-sinon over "plain" sinon because it integrates nicely with Mocha.

示例:

var expect = require('chai').expect;
require('mocha-sinon');

// Function to test, can also be in another file and as long as it's
// being called through some public interface it should be testable.
// If it's not in any way exposed/exported, testing will be problematic.
function privateFunction (time) {
  if (time < 12) { console.log('Good morning'); }
  if (time >= 12 && time <19) { console.log('Good afternoon'); }
  else { console.log('Good night!'); }
}

describe('privateFunction()', function() {

  beforeEach(function() {
    this.sinon.stub(console, 'log');
  });

  it('should log "Good morning" for hours < 12', function() {
    privateFunction(5);
    expect( console.log.calledOnce ).to.be.true;
    expect( console.log.calledWith('Good morning') ).to.be.true;
  });

  it('should log "Good afternoon" for hours >= 12 and < 19', function() {
    privateFunction(15);
    expect( console.log.calledOnce ).to.be.true;
    expect( console.log.calledWith('Good afternoon') ).to.be.true;
  });

  it('should log "Good night!" for hours >= 19', function() {
    privateFunction(20);
    expect( console.log.calledOnce ).to.be.true;
    expect( console.log.calledWith('Good night!') ).to.be.true;
  });

});

一个潜在的问题:一些摩卡记者也使用console.log，因此将其存根的测试可能不会产生任何输出.

One potential issue: some Mocha reporters use console.log as well, so the tests that stub it may not yield any output.

有一种解决方法，但也不理想，因为它将Mocha输出与privateFunction()输出混杂在一起.如果这不是问题，请用以下内容替换beforeEach():

There's a workaround, but it's not ideal either because it will intersperse Mocha output with the output from privateFunction(). If that's not a problem, replace beforeEach() with this:

beforeEach(function() {
  var log = console.log;
  this.sinon.stub(console, 'log', function() {
    return log.apply(log, arguments);
  });
});

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