{"id":486,"date":"2016-02-21T20:29:05","date_gmt":"2016-02-21T19:29:05","guid":{"rendered":"http:\/\/joost.vunderink.net\/blog\/?p=486"},"modified":"2016-02-28T10:31:41","modified_gmt":"2016-02-28T09:31:41","slug":"automated-software-testing-part-3-writing-tests-and-refactoring","status":"publish","type":"post","link":"https:\/\/joost.vunderink.net\/blog\/2016\/02\/21\/automated-software-testing-part-3-writing-tests-and-refactoring\/","title":{"rendered":"Automated software testing part 3: writing tests, and refactoring"},"content":{"rendered":"

Previous: part 2<\/a>\u00a0– Next: part 4<\/a><\/p>\n

In this post, we will look at the process of writing unit tests for existing code. In the process, we will be refactoring the code to make the tests easier and clearer – and to improve the code.<\/p>\n

The code\u00a0is in node.js<\/a> with the express framework<\/a>. However, the approach we will take is not language specific. Reading this post can help you even if you have never written any node.js code.<\/p>\n

This is a long post and would have been better as a screencast. When I have created that screencast, I’ll add a link to it in this post.<\/p>\n

You can also find the code below in the src\/unit-test-1<\/span>\u00a0\u00a0dir of my blog code repository<\/a>.<\/p>\n

Note: The code snippets contain a few things that should be done differently in production code. For example, using asynchronous fs calls (e.g. <\/em>fs.readFile<\/span>\u00a0 instead of <\/em>fs.readFileSync<\/span>\u00a0); using\u00a0<\/em>“use strict;”<\/span>\u00a0 ; and using modules like log4js<\/a>\u00a0and\u00a0sinon<\/a>.<\/em><\/p>\n

Step 1<\/h2>\n

This is the code we shall write tests for:<\/p>\n

\/\/ server.js\r\n\r\n\/\/ Express is a web framework for node.js.\r\nvar express = require('express');\r\n\r\n\/\/ Moment is a date manipulation library.\r\nvar moment = require('moment');\r\n\r\n\/\/ Fs is a core module of node.js to manipulate the file system.\r\nvar fs = require('fs');\r\n\r\nvar app = express();\r\n\r\n\/\/ When a http request is done on \/count\/start, execute this code.\r\n\/\/ req contains request information, which we are not using.\r\n\/\/ res is the response object.\r\napp.get('\/count\/start', function (req, res) {\r\n  \/\/ Read the server log file\r\n  var data = fs.readFileSync(__dirname + '\/server.log').toString();\r\n\r\n  \/\/ and count how many lines contain the words 'server started'.\r\n  var numStartLines = data\r\n    .split(\/\\r\\n|\\r|\\n\/)\r\n    .filter(function(line) { return \/server started\/.test(line); })\r\n    .length;\r\n\r\n  \/\/ Send a JSON answer that shows how many times the server has been started.\r\n  res.send({ numStart: numStartLines });\r\n});\r\n\r\nvar server = app.listen(64001, function () {\r\n  \/\/ When the server starts, log that it started.\r\n  var msg = moment().format('YYYY-MM-DD HH:mm:ss') + ' - server started\\n';\r\n  fs.appendFileSync(__dirname + '\/server.log', msg);\r\n  \r\n  var host = server.address().address\r\n  var port = server.address().port\r\n\r\n  console.log(\"Unit test 1 app v1 listening at http:\/\/%s:%s\", host, port)\r\n});\r\n<\/pre>\n
This code starts an HTTP server that listens on localhost:64001<\/span>\u00a0. It writes to a log file whenever it is started. On an HTTP request to http:\/\/localhost:64001\/count\/start<\/span>\u00a0, it returns a JSON structure that shows how many times the server has started. Like this:<\/p>\n
czapka:~$ curl localhost:64001\/count\/start\r\n{\"numStart\":5}<\/pre>\n
We want to test if the correct count is returned by our URL – so the code that is the second argument of app.get(‘\/count\/start’, function)<\/span>\u00a0. How can we do that?<\/p>\n
If we load server.js<\/span>\u00a0 in our test file, the server is actually started and the real log file is being used. This is not an option. Besides, running the server and testing the HTTP call is a\u00a0high level test – let’s test it on a lower level. To do this, we need to separate the count start function from the server itself.<\/p>\n
Step 2<\/h2>\n
We’ll create a count.js<\/span>\u00a0 file to put the count start functionality in. It looks like this:<\/p>\n
\/\/ count.js\r\n\r\nvar fs = require('fs');\r\n\r\nfunction countStart(req, res) {\r\n  var data = fs.readFileSync(__dirname + '\/server.log').toString();\r\n  var numStartLines = data\r\n    .split(\/\\r\\n|\\r|\\n\/)\r\n    .filter(function(line) { return \/server started\/.test(line); })\r\n    .length;\r\n  res.send({ numStart: numStartLines });\r\n}\r\n\r\nmodule.exports = {\r\n  countStart: countStart\r\n};\r\n<\/pre>\n
The app.get()<\/span>\u00a0 line in server.js<\/span>\u00a0 needs to be changed as well:<\/p>\n
\/\/ Modifications to server.js\r\n\r\nvar count = require('.\/count');\r\napp.get('\/count\/start', count.countStart);<\/pre>\n
Excellent. Now we can create count.spec.js<\/span>\u00a0 to test the new countStart<\/span>\u00a0 function. Let’s give it a shot. We’ll use the mocha framework<\/a> for testing and should<\/a> to check actual results against expected results.<\/p>\n
\/\/ count.spec.js\r\n\r\nrequire('should');\r\n\r\nvar count = require('.\/count');\r\n\r\ndescribe('countStart', function() {\r\n  it('should count the number of times the server was started', function() {\r\n    var req = ..?\r\n    var res = ..?\r\n    count.countStart(req, res);\r\n    something.should.equal(somethingElse);\r\n  });\r\n});\r\n<\/pre>\n
There are a few problems here.<\/p>\n