building unit tests correctly with visual studio 2013

Download Building unit tests correctly with visual studio 2013

Post on 28-Aug-2014

443 views

Category:

Software

0 download

Embed Size (px)

DESCRIPTION

Unit testing is now considered a mainstream practice, but that does not mean it is as common, pervasive or as well understood as it could or should be. Many programmers struggle with the quality of their tests and with the focus of their code. In this session we’ll learn how to write good unit testing code.

TRANSCRIPT

  • Building Unit Tests correctly with VS 2013
  • About.ME Senior Consultant @CodeValue Developing software (Professionally) since 2002 Mocking code since 2008 Test driven professional Blogger: http://blog.drorhelper.com
  • /* * You may think you know what the following code does. * But you dont. Trust me. * Fiddle with it, and youll spend many a sleepless * night cursing the moment you thought youd be clever * enough to "optimize" the code below. * Now close this file and go play with something else. */ // // Dear maintainer: // // Once you are done trying to 'optimize' this routine, // and have realized what a terrible mistake that was, // please increment the following counter as a warning // to the next guy: // // total_hours_wasted_here = 42 //
  • //This code sucks, you know it and I know it. //Move on and call me an idiot later. http://stackoverflow.com/questions/184618/what-is-the- best-comment-in-source-code-you-have-ever-encountered We fear our code! //Abandon all hope ye who enter beyond this point //When I wrote this, only God and I understood what I was doing //Now, God only knows // I dedicate all this code, all my work, to my wife, Darlene, who will // have to support me and our three children and the dog once it gets // released into the public. //The following 1056 lines of code in this next method //is a line by line port from VB.NET to C#. //I ported this code but did not write the original code. //It remains to me a mystery as to what //the business logic is trying to accomplish here other than to serve as //some sort of a compensation shell game invented by a den of thieves. //Oh well, everyone wants this stuff to work the same as before. //I guess the devil you know is better than the devil you don't.
  • If were afraid to change the very thing weve created, we failed as professionals Robert C. Martin
  • Legacy code
  • Code without tests is bad code... With tests, we can change the behavior of our code quickly and verifiably... Michael Feathers - Working effectively with legacy code
  • This is a unit test [Test] public void CheckPassword_ValidUser_ReturnTrue() { bool result = CheckPassword(user, pass); Assert.That(result, Is.True); } D
  • This is also a unit test [TestMethod] public void CheckPassword_ValidUser_ReturnTrue() { bool result = CheckPassword(user, pass); Assert.IsTrue(result); } D
  • A unit test is 1. Tests specific functionality 2. Clear pass/fail criteria 3. Good unit test runs in isolation
  • Unit testing is an iterative effort Unit testing is an iterative effort
  • Theres more to unit tests then just tests Written by the developer who wrote the code Quick feedback Avoid stupid bugs Immune to regression Change your code without fear In code documentation
  • 13 copyright 2008 trainologic LTD 13 One last reason Youre already Testing your code manually So why not save the time?
  • The cost of unit testing 120% 135% 115% 125% 0% 20% 40% 60% 80% 100% 120% 140% IBM: Drivers MS: Windows MS: MSN MS: VS Time taken to code a feature WithoutTDD Using TDD
  • The value of unit testing 61% 38% 24% 9% 0% 20% 40% 60% 80% 100% 120% 140% IBM: Drivers MS: Windows MS: MSN MS: VS Using Test Driven Design Time To Code Feature Defect density of team Major quality improvement for minor time investment
  • The cost of bugs 0 1 2 3 4 5 6 7 8 9 10 0% 20% 40% 60% 80% 100% Thousand$s %defectscreated Where does it hurt? % of Defects Introduced Cost to Fix a Defect The pain is here! This is too late
  • Supporting environment The team Development environment
  • The Team The team commitment is important Learn from test reviews Track results
  • Tools of the trade Server Dev Machine Source Control Build Server Test Runner Code CoverageBuild Script Unit Testing Framework Isolation Framework
  • Development environment Make it easy to write and run tests Unit test framework Test Runner Isolation framework Know where you stand Code coverage
  • Unit testing frameworks Create test fixtures Assert results Additional utilities Usually provide command-line/GUI runner http://en.wikipedia.org/wiki/List_of_unit_testing_frameworks
  • [Test] public void AddTest() { var cut = new Calculator(); var result = cut.Add(2, 3); Assert.AreEqual(5, result); } This is not a real unit test
  • Real code has dependencies Unit test Code under test Dependency Dependency
  • The solution - Mocking Fake object(s) Unit test Code under test Dependency
  • Isolation Replace production logic with custom logic We do this in order to Focus the test on one class only Test Interaction Simplify Unit test writing
  • What Mocking framework can do for you? Create Fake objects Set behavior on fake objects Verify method was called And more...
  • [Test] public void IsLoginOK_LoggerThrowsException_CallsWebService() { var fakeLogger = Isolate.Fake.Instance(); Isolate .WhenCalled(() => fakeLogger.Write("")) .WillThrow(new LoggerException()); var fakeWebService = Isolate.Fake.Instance(); var lm = new LoginManagerWithMockAndStub(fakeLogger,fakeWebService); lm.IsLoginOK("", ""); Isolate.Verify.WasCalledWithAnyArguments(() => fakeWebService.Write("")); }
  • Open source FakeItEasy Moq NMock3 nSubtitute Rhino Mocks Free MS Fakes Commercial Isolator JustMock
  • Moq 45% Rhino Mocks 23% None 9% FakeItEasy 6% Nsubstitute 6% Isolator 4% Moles 2% MS Fakes 2% JustMocks 2% Other 1% http://osherove.com/blog/2012/5/4/annual-poll-which-isolation-framework-do- you-use-if-any.html
  • Code Coverage So, What is a good code coverage?
  • Source Control Build Server Commit There you go Whats new? Build Agents We automatically get Error reports & logs New version installer Help files More
  • Build run at a Glance
  • How I failed unit testing my code Unit testing is great! Everything should be tested I can test almost everything Tests break all the time Unit testing is a waste of time
  • A good unit test should be: Easy to understand Trustworthy Robust Trust Your Tests!
  • Trustworthy means deterministic Problem I cannot re-run the exact same test if a test fails Solution Dont use Random in tests If you care about the values set them If you dont care about the values put defaults Do not use Sleep & time related logic fake it Use fake objects to force determinism into the test When possible avoid threading in tests.
  • Trustworthy also means not fragile Ideally A test would only fail if a bug was introduced OR Requirements changed
  • How to avoid fragile tests Dont test private/internal (most of the time) Fake as little as necessary Test only one thing (most of the time)
  • Readable unit tests Unit test intent should be clear! 1.What is being tested? 2.What is the desired outcome? 3.Why did test fail?
  • Learn to write clean tests [Test] public void CalculatorSimpleTest() { calc.ValidOperation = Calculator.Operation.Multiply; calc.ValidType = typeof (int); result = calc.Multiply(1, 3); Assert.IsTrue(result == 3); if (calc.ValidOperation == Calculator.Operation.Invalid) { throw new Exception("Operation should be valid"); } }
  • Or suffer the consequences! [Test] public void CalculatorSimpleTest() { var calc = new Calculator(); calc.ValidOperation = Calculator.Operation.Multiply; calc.ValidType = typeof (int); var result = calc.Multiply(-1, 3); Assert.AreEqual(result, -3); calc.ValidOperation = Calculator.Operation.Multiply; calc.ValidType = typeof (int); result = calc.Multip

Recommended

View more >