Test Driven Development (TDD) is a core practice in the SDLC, especially ones that run using the agile mindset and leverage the practices of eXtreme programming. Since its inception and rediscovery by Kent beck in the late 1990s, it has gained popularity among many software development teams. However, like any popular software development practices, teams lose interest in TDD overtime and drop the practice all together. The main reason behind this is practicing it "the wrong way". In this session, I present 7 anti-patterns that can ruin the TDD experience of a software development team. I also present how to counter these anti-patterns to fully leverage the benefits of TDD.

1. Ahmed Misbah - September 2022
TDD Anti-patterns
2022 edition

2. TDD Anti-patterns
Agenda
• About the speaker
• What is TDD?
• The anti-patterns
• References

3. TDD Anti-patterns
Agenda
➡ About the speaker
• What is TDD?
• The anti-patterns
• References

4. About the speaker
Role and previous talks
• Chief Software Engineer and Architect
• Speaker at:
‣ Delta Technopreneurs
‣ DevOpsDays Cairo
‣ AMECSE
‣ Orange DevTest Days
‣ GDG
‣ JDC

5. About the speaker
Topics of interest
• DevOps
• Agile and Lean
• Cloud-Native Apps and beyond
• Software Architecture
• Java
• FOSS
• Arti
fi
cial Intelligence and ML

6. About the speaker
Experience
• 9 years at Orange Innovation Egypt
• Delivered two award winning innovative
solutions
• Worked at two startups
• Helped many others!
• Winner of Dell Hacktrick 2022 UI/UX track
• MSc. degree in ML and many other
professional certi
fi
cations
Nile University
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Has successfully completed the program of study
and fulfilled the requirements for
BigData & Data Science Diploma
for the period from October 2015 to July 2016
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7. TDD Anti-patterns
Agenda
• About the speaker
➡ What is TDD?
• The anti-patterns
• References

8. Martin Fowler
“Test-Driven Development (TDD) is a technique for building software that
guides software development by writing tests. It was developed by Kent
Beck in the late 1990's as part of Extreme Programming. In essence you
follow three simple steps repeatedly:
• Write a test for the next bit of functionality you want to add.
• Write the functional code until the test passes.
• Refactor both new and old code to make it well structured.”

9. TDD Anti-patterns
Agenda
• About the speaker
• What is TDD?
➡ The anti-patterns
• References

10. TDD Anti-patterns
7 anti-patterns
1. No test list
2. No refactoring
3. No pair/mob programming
4. No particular school
5. No integration
6. No mutation testing
7. Practice + technology before theory

11. (1) No test list

12. Kent Beck
“Test-Driven Development By Example”, Chapter 25 - Test Driven Development
Patterns
“What should you test? Before you begin, write a list of all the
tests you know you will have to write. The first part of our
approach to dealing with programming stress is never to take
a step forward unless we know where our foot is going to
land. When we sit down to a programming session, what is it
we intend to accomplish?”

14. No test list
The true Red-Green-Refactor
• Invented by James Shore in 2005 (link)
• Steps:
1. Think: Figure out what test will best move
your code towards completion. (Take as
much time as you need. This is the hardest
step for beginners.)
2. Red
3. Green
4. Refactor
5. Repeat

15. “The Coding Dojo Handbook”, Section 3

16. No test list
How to write a test list?
• Pair/mob with testers
• Use test design techniques
Sample test list by Kent Beck

17. (2) No refactoring

18. Martin Fowler
“The most common way that I hear to screw up TDD is
neglecting the third step. Refactoring the code to keep it clean
is a key part of the process, otherwise you just end up with a
messy aggregation of code fragments. (At least these will
have tests, so it's a less painful result than most failures of
design.)”

19. Refactoring
What do we do in the refactor phase?
• It’s when you remove duplication - Kent Beck
• It’s when you sanitize the code smells - Martin
Fowler
• It’s when you apply patterns - Joshua Kerievsky
“TDD, Where Did it All Go Wrong” video

20. Refactoring
It’s all about design
• “There is no design phase in TDD. Using TDD, design is inverted and distributed”
• “TDD completely inverts the accepted ordering of ‘design-code-test'”
• “TDD just puts the design after the test and the code. Refactoring is pure design.”
“Test-Driven Development” eLearning Album - Industrial Logic
Code
Design Test Refactor
Code
Test
Design/
Refactor

21. (3) No pair / mob programming

22. No pair / mob programming
Issues with working solo in TDD
Learning curve (technologies, recommended
practices, etc.)
Knowledge sharing (technologies, recommended
practices, business, test list, etc.)
Collective ownership (of production code and tests)

23. (4) No particular school

24. No particular school
Di
ff
erent Architectures
“Domain-speci
fi
c Semantic Web-based Information Systems - Any Progress?” paper

25. No particular school
The schools of TDD
• Classicist (aka. Chicago or Detroit school of TDD):
‣ Inside-out
‣ Tests behavior
‣ No mocks
• Mockist (aka. London school of TDD)
‣ Outside-in
‣ Tests structure?
‣ Uses mocks

26. No particular school
Understand the schools
• A beginners explanation of the Chicago & London approaches
• London vs. Chicago
• Chicago TDD vs London TDD – Which one is should you use?
• London vs. Chicago by Robert (Bob) Martin and Sandro Mancuso

27. (5) No integration

29. No integration
Microtesting
• Invented by Mike (GeePaw) Hill in 2011 (link)
• The Four-Beat Cycle:
1. RED
2. GREEN
3. REFACTOR
4. INTEGRATE: We commit our changes,
including the new micro-test(s), to the
source vault.

30. (6) No mutation testing

31. Alex Bunardzic
“Two things surprised me a lot recently:
1. Number of experienced TDDers who told me they fail to see
value in Mutation testing
2. Number of experienced TDDers who told me they fail to see
value in TCR”

32. No mutation testing
Why Mutation Tests?
• Traditional test coverage (i.e., line,
statement, branch, etc.) measures only
which code is executed by your tests. It
does not check that your tests are able
to detect faults in the executed code. It is
therefore only able to identify code that is
not tested
• As it can detect whether each statement is
meaningfully tested, mutation testing is
the gold standard against which all other
types of coverage are measured
Source link

34. (7) Practice + technology before
theory

35. Ahmed Galal - Mobile UX session - 2012
“Experience = Knowledge (i.e., Theory) + Practice”

36. Practice + technology before theory
Experience, Theory and Practice
• Experience is often used interchangeably with practice.
• However, true experience is gained by both learning knowledge and theory
and applying it (i.e., practice)

37. W. Edwards Deming - “The New Economics for Industry, Government, Education” book
“Experience by itself teaches nothing... Without theory,
experience has no meaning. Without theory, one has no
questions to ask. Hence, without theory, there is no
learning.”

38. Practice + technology before theory
Knowledge then practice + technology
• Beginners start with courses that teach technologies without diving deep into
the theory and recommended practices
• Beginners should read:
- The three laws of TDD - “Clean Code” by Robert (Bob) C. Martin
- F.I.R.S.T properties - “Clean Code” by Robert (Bob) C. Martin
- Test Desiderata - Kent Beck
- TDD Manifesto

39. Thank you!

40. References

41. References

43. Book a free call to arrange a workshop
• Introduction to TDD
• Advanced topics in TDD
• TDD and refactoring workshop
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