Beyond Unit Testing: The Real Value of Test-Driven Development

Transcript

1. Beyond Unit Testing The Real Value of Test-Driven Development Anthony Sciamanna Senior Consultant Industrial Logic April 16, 2025
2. Anthony Sciamanna Technical Agile & Lean Coach, Trainer, Blogger & Organizer of the PhillyXP user group. Website: https://anthonysciamanna.com Email: anthony@industriallogic.com Twitter: @asciamanna https://www.meetup.com/phillyxp/
3. TDD Refresher Image by Industrial Logic Senior Consultant - Tim Ottinger @asciamanna anthonysciamanna.com Add / Update a test Make it work Make it clean
4. A Tale of Two Hats @asciamanna anthonysciamanna.com Adding Functionality Refactoring Writing a failing test or making it pass Small, behavior preserving code improvements You can only wear one hat at a time! https://martinfowler.com/articles/workflowsOfRefactoring/#2hats
5. @asciamanna anthonysciamanna.com TDD Refresher Image courtesy of Bill Wake – TDD, TCR, and Frequent Commits
6. TDD Refresher @asciamanna anthonysciamanna.com
7. Let’s go back in time! @asciamanna anthonysciamanna.com
8. TD Refresher A Very Brief History of TDD 1994 Kent Beck releases the first version of the SUnit framework for Smalltalk @asciamanna anthonysciamanna.com
9. TD Refresher A Very Brief History of TDD 1994 1995 Kent demos TDD to Ward Cunningham at OOPSLA Austin in October. Details of the C3 Project start being publicized Kent Beck releases the first version of the SUnit framework for Smalltalk @asciamanna anthonysciamanna.com
10. TD Refresher A Very Brief History of TDD 1994 1995 1997 Kent demos TDD to Ward Cunningham at OOPSLA Austin in October. Details of the C3 Project start being publicized Kent Beck releases the first version of the SUnit framework for Smalltalk On a flight from Zurich to Atlanta (OOPSLA ‘97) Erich Gamma and Kent Beck create JUnit for Java @asciamanna anthonysciamanna.com
11. TD Refresher A Very Brief History of TDD 1994 1995 1997 1999 Kent demos TDD to Ward Cunningham at OOPSLA Austin in October. Details of the C3 Project start being publicized Kent Beck releases the first version of the SUnit framework for Smalltalk On a flight from Zurich to Atlanta (OOPSLA ‘97) Erich Gamma and Kent Beck create JUnit for Java Kent releases Extreme Programming Explained @asciamanna anthonysciamanna.com
12. TDD Is a Testing Practice @asciamanna anthonysciamanna.com
13. @asciamanna anthonysciamanna.com I don’t care if people write tests first or last. As long as they get written. - Anonymous Tech Lead
14. @asciamanna anthonysciamanna.com Ignores Design and Workflow Benefits of TDD
15. Benefits of TDD @asciamanna anthonysciamanna.com
16. Benefits of TDD @asciamanna anthonysciamanna.com Externally Visible Artifacts Test Suite
17. Benefits of TDD @asciamanna anthonysciamanna.com Externally Visible Artifacts Test Suite
18. Benefits of TDD Externally Visible Artifacts @asciamanna anthonysciamanna.com Software Design Test Suite
19. Benefits of TDD Externally Visible Artifacts @asciamanna anthonysciamanna.com Developer Workflow Software Design Test Suite
20. Benefits of TDD Externally Visible Artifacts @asciamanna anthonysciamanna.com Developer Workflow Software Design Test Suite
21. Test Suite Benefits Why we prefer TDD-style tests over Test After Tests
22. Test Suite Quality Production Code Quality Test suite quality influences production code quality and vice-versa @asciamanna anthonysciamanna.com
23. You Can’t Write Good Tests for Bad Code • Wrapping untestable code in unit tests results in brittle, low-quality tests, that suffer from false failures • Test-first practices enable writing high quality production code and high- quality tests Markus Spiske for Tech Daily @asciamanna anthonysciamanna.com
24. @asciamanna anthonysciamanna.com
25. The Test Pyramid Microtests / Unit tests Integration / Acceptance tests E2E / UI tests As scope increases, detail should decrease Increase in: • Cost to develop and maintain • Execution time • Possibility of false negatives • Time to identify source of issue @asciamanna anthonysciamanna.com https://anthonysciamanna.com/2019/10/20/avoiding-automated-testing-pitfalls.html More integration More isolation
26. The TDD Quality Cycle Test Suite Production Code 2. Code under test must be testable (loosely coupled) Refactoring Refactoring 3. Enables tests to be small, precise, fast, isolated and independent Virtuous Cycle 1. We start in the test @asciamanna anthonysciamanna.com
27. Microtest A short, simple, fast, isolated*, test that probes the behavior of a single class *Isolated does not mean we have to mock every dependency anthonysciamanna.com @asciamanna
28. Microtests Don’t Access a network Access a database Access the filesystem Depend on other tests Require a complex environment to run in @asciamanna anthonysciamanna.com
29. FIRST Properties of Microtests https://medium.com/pragmatic-programmers/unit-tests-are-first-fast-isolated-repeatable-self-verifying-and-timely-a83e8070698e Created by Industrial Logic Senior Consultants Tim Ottinger & Brett Schuchert
30. S O S anthonysciamanna.com @asciamanna
31. Small O S anthonysciamanna.com @asciamanna
32. Small Obvious S anthonysciamanna.com @asciamanna
33. Small Obvious Simple anthonysciamanna.com @asciamanna
34. Small ~12 LOC or less per test @asciamanna anthonysciamanna.com
35. Obvious anthonysciamanna.com @asciamanna
36. Arrange Act Assert anthonysciamanna.com @asciamanna Arrange-Act-Assert
37. anthonysciamanna.com @asciamanna
38. Standardize common test constructs Create the object under test in Setup Standard name result to be asserted Standard name for object under test anthonysciamanna.com @asciamanna
39. Simple Avoid branching and flow control logic in tests anthonysciamanna.com @asciamanna
40. How To Stop Hating Your Test Suite Logic in tests confuses the story of what’s being tested. Test-scoped logic is hard to read and errors are easy to miss. - Justin Searls, Co-founder Test Double anthonysciamanna.com @asciamanna
41. How To Stop Hating Your Test Suite Test code is untested code! - Justin Searls, Co-founder Test Double anthonysciamanna.com @asciamanna
42. anthonysciamanna.com @asciamanna Test After Test First Manual testing often takes precedence Unit testing at end tends to be skipped to hit deadlines All code is tested as it is created or modified Feels like busy work if code is manually tested and considered “done” The test is the path to changing the system Code is not influenced by tests to be testable Code is influenced by the tests to be testable Tests don’t serve as feedback loops Tests are continuous feedback loops, supports refactoring and software design Tests don’t get refactored – created at end Tests are continuously refactored Tests are less comprehensive when added at end Tests are more comprehensive when added with each code change Coverage as a build gate often required (commonly 70% coverage) Coverage metrics unnecessary Tests implementation details Tests behavior VS.
43. Software Design Benefits Tests guiding quality software design
44. TDD Disclaimer TDD influences design quality But it’s not a magic wand! anthonysciamanna.com @asciamanna
45. TDD Disclaimer TDD influences design quality High Cohesion Loose Coupling Small Classes Small Methods anthonysciamanna.com @asciamanna
46. TDD Disclaimer TDD provides a mechanism for learning software design High Cohesion Loose Coupling Small Classes Small Methods anthonysciamanna.com @asciamanna
47. Practitioners still need to understand the concepts of software design High Cohesion Loose Coupling Code Smells Design Patterns SOLID Refactoring Encapsulation GRASP Connascence anthonysciamanna.com @asciamanna TDD Disclaimer
48. Test-Driven Development Refactoring Legacy Code Techniques Microtesting / Test Suite Design Code Smells Design Patterns Cohesion & Coupling SOLID Continuous Integration Continuous Delivery Evolutionary Design Collaborative Development Iterative Development anthonysciamanna.com @asciamanna
49. Microtests are litmus tests for software design quality @asciamanna anthonysciamanna.com
50. Examples @asciamanna anthonysciamanna.com
51. Too Much Test Setup Too Many Dependencies Too Many Arguments Arguments are Too Complex Code Under Test Doing Too Much anthonysciamanna.com @asciamanna
52. Multiple ‘Act’ Steps Temporal Coupling Exists Complicated API Client needs to know too much about object under test Too Many Steps to Invoke Method Under Test anthonysciamanna.com @asciamanna
53. Too Many Asserts Returning too complex of a type Code under test doing too much anthonysciamanna.com @asciamanna
54. Too Many Test Cases Too much branching logic Code under test is doing too much anthonysciamanna.com @asciamanna
55. Client-First Design / Outside-In TDD enables software design from a client’s perspective Leads to better designed interfaces between objects anthonysciamanna.com @asciamanna
56. Refactoring into design yields a better design than Big Design Up Front Requirements Design Code Test Waterfall Mindset Requirements Test Code Design (Refactor) (Test-Driven) Agile Mindset Slide courtesy of Mike Rieser (@MichaelRieser) anthonysciamanna.com @asciamanna JIT (re)design design design design design
57. Developer Workflow Benefits Short, fast feedback cycles improve productivity
58. Nearly instantaneous feedback loops anthonysciamanna.com @asciamanna
59. Fast Feedback Loops key to developer productivity & high performing teams anthonysciamanna.com @asciamanna
60. anthonysciamanna.com @asciamanna
61. Resilient to Interruptions anthonysciamanna.com @asciamanna
62. TDD-created Microtests are save states for system functionality anthonysciamanna.com @asciamanna
63. anthonysciamanna.com @asciamanna
64. BIG PROBLEM @asciamanna anthonysciamanna.com
65. BIG PROBLEM @asciamanna anthonysciamanna.com Great software is created by GREAT TEAMS not heroic, rockstar, 10X developers working in isolation
66. BIG PROBLEM @asciamanna anthonysciamanna.com Software development is a communication game Communication is the professional developer’s first order of business. Perhaps you thought that ‘getting it working’ was the first order of business for a professional developer. I hope by now, however, this book has disabused you of that idea. - Robert Martin, Clean Code
67. System is always in a working state anthonysciamanna.com @asciamanna
68. Tiny Validations anthonysciamanna.com @asciamanna
69. https://www.geepawhill.org/2018/04/14/tdd-the-lump-of-coding-fallacy/ anthonysciamanna.com @asciamanna GeePaw Hill – TDD & the Lump of Coding Fallacy
70. https://www.geepawhill.org/2018/04/14/tdd-the-lump-of-coding-fallacy/ anthonysciamanna.com @asciamanna GeePaw Hill – TDD & the Lump of Coding Fallacy
71. https://www.geepawhill.org/2018/04/14/tdd-the-lump-of-coding-fallacy/ anthonysciamanna.com @asciamanna GeePaw Hill – TDD & the Lump of Coding Fallacy
72. https://www.geepawhill.org/2018/04/14/tdd-the-lump-of-coding-fallacy/ anthonysciamanna.com @asciamanna GeePaw Hill – TDD & the Lump of Coding Fallacy
73. Mental Benefits of TDD One of the hardest things to communicate about Test-Driven Development is the mental state it puts you in…On the original C3 project…progress was steady and unhurried; because it was unhurried it seemed slow, but looking back on how much we got done, it was clear that despite the unhurried feeling progress was really fast. “ ” anthonysciamanna.com @asciamanna
74. Mental Benefits of TDD Concrete and visible progress on small incremental goals @asciamanna anthonysciamanna.com
75. Mental Benefits of TDD @asciamanna anthonysciamanna.com Achieving Profluence
76. Mental Benefits of TDD Little or no time spent in the debugger or on repetitive, time consuming manual checks anthonysciamanna.com @asciamanna
77. Learning TDD will help improve software design, developer workflow, increases developer happiness, and it’s a lot of fun! https://geepawhill.org https://github.com/testdouble/contributing-tests/wiki Test Double – Contributing Tests Wiki Industrial Logic eLearning https://www.industriallogic.com/elearning/ anthonysciamanna.com @asciamanna
78. http://bit.ly/beyond-unit-testing-2025 @asciamanna anthonysciamanna.com
79. Attributes • Pygmy Marmoset - https://www.flickr.com/photos/gopak/39889008421 • SOS - https://www.flickr.com/photos/itupictures/16654290295 • Darts - https://www.flickr.com/photos/mike-burns/374198933 • Quote - Nick Youngson CC BY-SA 3.0 • Magician - Photo by Pierrick VAN-TROOST on Unsplash • Litmus test - https://commons.wikimedia.org/wiki/File:Blue_and_red_litmus_paper.JPG • Self-operating napkin - https://upload.wikimedia.org/wikipedia/commons/8/88/Self- operating_napkin_%28Rube_Goldberg_cartoon_with_caption%29.jpg • Glass Cockpit - https://upload.wikimedia.org/wikipedia/commons/9/9f/C-5M_Cockpit.jpg • Public Domain, https://commons.wikimedia.org/w/index.php?curid=2466026 • Stack of Papers - https://upload.wikimedia.org/wikipedia/commons/b/b6/FileStack_retouched.jpg • El Diablo - https://en.wikipedia.org/wiki/Fire_Ball#/media/File:El_Diablo_Roller_Coaster.jpg • Creative Commons license: https://creativecommons.org/licenses/by/2.0/