Building unit tests correctly with visual studio 2013

2,135 views
1,966 views

Published on

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.

Published in: Software, Technology, Education
0 Comments
1 Like
Statistics
Notes
  • Be the first to comment

No Downloads
Views
Total views
2,135
On SlideShare
0
From Embeds
0
Number of Embeds
15
Actions
Shares
0
Downloads
27
Comments
0
Likes
1
Embeds 0
No embeds

No notes for slide
  • Taken from http://research.microsoft.com/en-us/projects/esm/nagappan_tdd.pdf

    Realizing quality improvement through test driven development: results and experiences of four industrial teams
    Published online: 27 February 2008
  • Explain about good places to start using unit tests
  • Building unit tests correctly with visual studio 2013

    1. 1. Building Unit Tests correctly with VS 2013
    2. 2. About.ME • Senior Consultant @CodeValue • Developing software (Professionally) since 2002 • Mocking code since 2008 • Test driven professional • Blogger: http://blog.drorhelper.com
    3. 3. /* * 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 //
    4. 4. //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.
    5. 5. “If we’re afraid to change the very thing we’ve created, we failed as professionals” Robert C. Martin
    6. 6. Legacy code
    7. 7. “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”
    8. 8. This is a unit test [Test] public void CheckPassword_ValidUser_ReturnTrue() { bool result = CheckPassword(“user”, “pass”); Assert.That(result, Is.True); } D
    9. 9. This is also a unit test [TestMethod] public void CheckPassword_ValidUser_ReturnTrue() { bool result = CheckPassword(“user”, “pass”); Assert.IsTrue(result); } D
    10. 10. A unit test is… 1. Tests specific functionality 2. Clear pass/fail criteria 3. Good unit test runs in isolation
    11. 11. Unit testing is an iterative effort Unit testing is an iterative effort
    12. 12. There’s 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. 13. 13 copyright 2008 trainologic LTD 13 One last reason You’re already Testing your code – manually So why not save the time?
    14. 14. 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
    15. 15. 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
    16. 16. 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…
    17. 17. Supporting environment • The team • Development environment
    18. 18. The Team • The team commitment is important • Learn from test reviews • Track results
    19. 19. Tools of the trade Server Dev Machine Source Control Build Server Test Runner Code CoverageBuild Script Unit Testing Framework Isolation Framework
    20. 20. Development environment • Make it easy to write and run tests – Unit test framework – Test Runner – Isolation framework • Know where you stand – Code coverage
    21. 21. 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
    22. 22. [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
    23. 23. Real code has dependencies Unit test Code under test Dependency Dependency
    24. 24. The solution - Mocking Fake object(s) Unit test Code under test Dependency
    25. 25. 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
    26. 26. What Mocking framework can do for you? • Create Fake objects • Set behavior on fake objects • Verify method was called • And more...
    27. 27. [Test] public void IsLoginOK_LoggerThrowsException_CallsWebService() { var fakeLogger = Isolate.Fake.Instance<ILogger>(); Isolate .WhenCalled(() => fakeLogger.Write("")) .WillThrow(new LoggerException()); var fakeWebService = Isolate.Fake.Instance<IWebService>(); var lm = new LoginManagerWithMockAndStub(fakeLogger,fakeWebService); lm.IsLoginOK("", ""); Isolate.Verify.WasCalledWithAnyArguments(() => fakeWebService.Write("")); }
    28. 28. Open source • FakeItEasy • Moq • NMock3 • nSubtitute • Rhino Mocks Free • MS Fakes Commercial • Isolator • JustMock
    29. 29. 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
    30. 30. Code Coverage So, What is a good code coverage?
    31. 31. Source Control Build Server Commit There you go What’s new? Build Agents We automatically get •Error reports & logs •New version installer •Help files •More…
    32. 32. Build run at a Glance
    33. 33. 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 
    34. 34. A good unit test should be: • Easy to understand • Trustworthy • Robust Trust Your Tests!
    35. 35. Trustworthy means deterministic Problem • I cannot re-run the exact same test if a test fails Solution • Don’t use Random in tests – If you care about the values set them – If you don’t 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.
    36. 36. Trustworthy also means not fragile Ideally A test would only fail if a bug was introduced OR Requirements changed
    37. 37. How to avoid fragile tests • Don’t test private/internal (most of the time) • Fake as little as necessary • Test only one thing (most of the time)
    38. 38. 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?
    39. 39. 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"); } }
    40. 40. 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.Multiply(1, 3); Assert.IsTrue(result == 3); if (calc.ValidOperation == Calculator.Operation.Invalid) { throw new Exception("Operation should be valid"); } calc.ValidOperation = Calculator.Operation.Multiply; calc.ValidType = typeof (int); result = calc.Multiply(10, 3); Assert.AreEqual(result, 30); }
    41. 41. Writing a good unit test [Test] public void Multiply_PassTwoPositiveNumbers_ReturnCorrectResult() { var calculator = CreateMultiplyCalculator(); var result = calculator.Multiply(1, 3); Assert.AreEqual(result, 3); }
    42. 42. So what about code reuse Readability is more important than code reuse • Create objects using factories • Put common and operations in helper methods • Use inheritance – sparsely
    43. 43. Avoid logic in the test (if, switch etc.) Problem • Test is not readable • Has several possible paths • High maintain cost
    44. 44. Tests should be deterministic Solution • Split test to several tests – one for each path – If logic change it’s easier to update some of the tests (or delete them) • One Assert per test rule
    45. 45. How to start with unit tests 1. Test what you’re working on – right now! 2. Write tests to reproduce reported bug 3. When refactoring existing code – use unit tests to make sure it still works. 4. Delete obsolete tests (and code) 5. All tests must run as part of CI build

    ×