Exploring alternatives is part of the design process. TDD is a way to do incremental design, or design while you write code. So can we use TDD to explore design alternatives? Turns out, I've seen a lot of design exploration during the 30+ code retreats I facilitated and attended. While I don't have a definite proof, it seems that TDD could be used for this purpose.

1. ExploringDesignAlternativesusingTDD

2. How do you design software?

3. Waystodesignsoftware
● Sketch a diagram (hopefully not UML)
● Think about the problem
● Write code (prototype)
● Review with other people, or work together

4. Why do we design software?

5. WhyDesignSoftware?

6. What is design?

7. Designis...
“Conceiving and giving
form to artifacts that
solve problems.”
Karl Ulrich
http://www.ulrichbook.org/

8. Designis...
Conceiving and giving form to artifacts that
solve problems
within constraints.
The primary constraint for software is need for
quick change.

9. GeneralDesignProcess

10. ExploringDesignAlternatives
Source: Apollo Paul Paredes

11. Software design:
What are the artifacts?

12. OOPArtifacts
● Classes
– List of methods
● Methods
– Names
– Parameter lists
● Collaboration between objects => contracts

13. Do you explore design alternatives?
How?

14. ExploringDesignAlternatives
● On paper
● By writing code

15. What's this got to do with TDD?

16. TDDis...
A way of doing incremental design
(design while writing code)

17. IncrementalDesign
Define examples of inputs – outputs
Implement
particular cases
Extract abstractions
aka generalize solution
aka design

18. Design is creation of artifacts that solve problems
Software design is the creation of classes,
methods etc. that solve a problem
Exploring design alternatives is part of the design
process
One way to explore an alternative is to build it
TDD is a method to design software while writing
code

19. How about using TDD as way to explore design
alternatives?

20. Turns out, I've seen a lot of exploration with TDD

21. Coderetreat
● One day
● 6 sessions, 45'
● Pair program, TDD
● Delete code, change
pair after session
● Use constraints
Code Retreat #1 in Europe
Attended / facilitated: ~30 code retreats

22. Inoticedatcoderetreatsthat...
How you start and the constraints you set may
change the final design.

23. How to start?

24. Vary:numberofdesignentities
TDD As If you meant it → 0 entities
.
.
.
n entities

25. Startfromexistingentities
● Must have a certain class
● Can't modify a certain class

26. Use different constraints

27. Constraints
● Pure functions
● Don't use data structures
● Use only events to communicate between
objects

28. Paradigm
● Only OOP
● Only Functional Programming

29. Conclusion
TDD can be used to explore design alternatives.

30. Thankyou!
Alexandru Bolboaca
Coach and Trainer at MozaicWorks
Contact me:
@alexboly
alex.bolboaca@mozaicworks.com
Remote pair with me
Come at code and beer!