stdout mock

我们知道console.log是放到process.stdout里打印日志的方法,那么在单元测试里怎么测试呢?

这里给出一个机遇mocha的测试

思路很简单

• 通过captureStream方法来拦截stdout
• 通过captureStream#captured获取stdout内容

代码如下

var assert = require('chai').assert;
var expect = require('chai').expect;
require('chai').should();
var console = require('../index');
function captureStream(stream){
 var oldWrite = stream.write;
 var buf = '';
 stream.write = function(chunk, encoding, callback){
 buf += chunk.toString(); // chunk is a String or Buffer
 oldWrite.apply(stream, arguments);
 }
 return {
 unhook: function unhook(){
 stream.write = oldWrite;
 },
 captured: function(){
 return buf;
 }
 };
}
describe('Console', function(){
	var hook;
	
 before(function() {
 // runs before all tests in this block
 })
 after(function(){
 // runs after all tests in this block
 })
 beforeEach(function(){
 // runs before each test in this block
		hook = captureStream(process.stdout);
 })
 afterEach(function(){
 // runs after each test in this block
		hook.unhook(); 
 })
 describe('#debug()', function(){
 it('should return a string when debug = true;', function(){
			console.debug = true;
			console.log("debug = true;");
 
			assert.equal(hook.captured(),'debug = true;\n');
 })
		
 it('should return empty string when debug = false;', function(){
			console.debug = false;
			console.log("debug = true;");
 	assert.equal(hook.captured(),'');
 })
 })
})

正摸不著头绪,原来就这样,长知识了!