The document describes a coding dojo event where participants will work in pairs using test-driven development and pair programming to solve the problem of programming a Mars rover to navigate a grid based on input commands. The rover must wrap around the grid, detect obstacles, and report its position and any obstacles encountered. Participants will work through introductions, coding exercises, and retrospectives while focusing on best practices like improving existing code rather than deleting it.

1. Coding Dojo:
Mars Rover
Oct. 2014
Peter Kofler, ‘Code Cop’
@codecopkofler
www.code-cop.org
Copyright Peter Kofler, licensed under CC-BY.

2. PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY
Peter Kofler
• Ph.D. (Appl. Math.)
• Professional Software
Developer for 15 years
• “fanatic about code quality”
• I help development teams

3. Coding Dojo?
Expectations?

4. PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY
Coding Dojo Mindset
● Safe place outside
work
● We are here to learn
● Need to slow down
● Focus on doing it right
● Collaborative Game

5. PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY
Two Basic Rules
● Collaborative = Pair Programming
● “Randori“ (pairing on the projector)
● or programming in pairs
● Test Driven Development
● think about tests
● write the test first

6. PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY
(Maybe Some) Constraints
● Challenges during a dojo or coderetreat.
● Moving to the extreme is a way of learning
● Examples
● Missing Tool (No Mouse, …)
● Missing Feature (No IFs, …)

7. PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY
Dojo Structure
● Introduction 15'
● Coding 45'
● Interim (Retrospective) 15'
● Break 10'
● Coding 45'
● Retrospective 15'

8. PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY
Assignment

9. PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY
Mars Rover
● Develop an API that moves a rover around on a grid.
● You are given the initial starting point (x,y) of a rover and
the direction ('N','S','E','W') it is facing.
● The rover receives a character array of commands.
● Move the rover forward/backward ('f','b').
● Turn the rover left/right ('l','r').
● Wrap the grid. (Planets are spheres after all.)
● Detect obstacles before each move to a new square. If a
sequence of commands encounters an obstacle, the rover
moves up to the last possible point and reports obstacle.

10. PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY
Mars Rover Example
● The rover is on a
100x100 grid
● at location (0, 0),
● facing "N"ORTH.
● The rover is given
commands "ffrff"
● and should end up
at (2, 2).
r f f
f
f
(0,0)
N
(2,2)

11. PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY
Remember the Rules!

12. PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY
Pair Programming & TDD
● regular Pair Programming
– do not talk for too long
– do not interrupt the other
– no “keyboard hugging“
● use TDD (or at least “sort of” TDD)
– write a test before you write code
– refactor mercilessly
– no debugger

13. PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY
With a Constraint

14. PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY
“Yes, and ...“
● When working in pairs none of the pairs
is allowed to delete the code of the other
person.
● We are looking for a common solution,
that both of the pairs will agree.
● Learn to build on top of the ideas
already presented.

15. PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY
“Yes, and ...“ Rules
● improve existing code of the other
● can not delete code of the other
● whenever one tries to delete code, say:
“You should improve the existing one.
Please go back and say Yes, and… I will do…”
● Can not be angry on request of not deleting code.
● Only unused code can be deleted.
● Both must agree that the code can be deleted.

16. PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY
Prepare
● Find a pair.
● Choose a programming language.
● Set up the environment.
● Create new project.
● Add testing framework.
● Check requirements.
● Implement Mars Rover.

17. Don't Focus on
Getting it Done.
F0cus on Doing
It Perfectly.

18. → Practice

19. PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY
Short Closing Circle
● How did it work out?
● How do you feel?
● What did you
learn and want
to share with
the group?

20. PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY
Full Closing Circle
● What did you learn today?
● What surprised you today?
● What will you do
differently in the
future?

21. PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY
Global Day of Code Retreat
● A world-wide event celebrating passion
and software craftsmanship.
● GDCR 2014:
15th November
● Follow #GDCR14
http://globalday.coderetreat.org/

22. PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY
Peter Kofler
@codecopkofler
www.code-cop.org
Game by
Adrian Bolboaca
@adibolb
http://blog.adrianbolboaca.ro/2013/12/pair-programming-game-yes-and/

23. PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY
CC Images
● Rover Selfie http://www.flickr.com/photos/gsfc/7971341456
● Dojo
http://www.flickr.com/photos/49715404@N00/3267627038/
● Todos
http://www.flickr.com/photos/kylesteeddesign/3724074594/
● Curiosity http://www.flickr.com/photos/mendhak/8162305237
● Rule http://www.flickr.com/photos/phunk/4188827473
● Model http://www.flickr.com/photos/eldave/8430367749
● Wants you http://www.flickr.com/photos/shutter/105497713/