Peter Kofler led a coding dojo session on outside-in test-driven development (TDD) for a bank optical character recognition (OCR) assignment. The assignment asked participants to write a program to parse account numbers from an OCR file containing entries with account numbers represented using pipes and underscores. Kofler emphasized learning outside one's work environment, focusing on quality over speed, and improving through collaboration and reflection.

1. Coding Dojo Vienna:
Bank OCR Outside-In
Session 20150428
#CodingDojoVie
Peter Kofler, ‘Code Cop’
@codecopkofler
www.code-cop.org
Copyright Peter Kofler, licensed under CC-BY.

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

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

4. “London” Constraint*
PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY
*) London School TDD is Outside-In but Classic TDD can be as well

5. Outside-In TDD
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build the system from the "outside-in",
following the user interaction
through all the parts of the system
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(maybe) create a Guiding Test
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start with top level interactions/collaborators
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create fake dependencies or mock them
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implement using TDD until all tests green
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move "inside" to previously faked collaborator
PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY

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

7. Bank OCR
●
You work for a bank, which has a machine to assist in reading
letters. The machine scans the paper documents, and produces
a file with a number of entries which each look like this:
····_··_·····_··_··_··_··_·
··|·_|·_||_||_·|_···||_||_|
··||_··_|··|·_||_|··||_|·_|
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Each entry is 4 lines long, each line has 27 characters. The first
3 lines contain an account number written using pipes and
underscores, and the fourth line is blank. Each account
number should have 9 digits, all of which should be in the
range 1-9.
●
Write a program that can take this file and parse it into actual
account numbers.
PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY

8. Prepare
●
Find a pair.
●
Choose a programming language.
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Java: https://bitbucket.org/pkofler/bankocr-kata-setup
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JS: https://bitbucket.org/carlosble/bankocr-kata
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Py: http://technivore.org/posts/2013/12/23/coding-kata-bank-ocr.html
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See BankOcrTest.java (failing test)
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guiding test as starting point.
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Work through outer API
PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY

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

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

11. Peter Kofler
@codecopkofler
www.code-cop.org
PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY

12. CC Images
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Bank https://www.flickr.com/photos/bigmacsc99/4325336251
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Dojo
http://www.flickr.com/photos/49715404@N00/3267627038/
●
London https://www.flickr.com/photos/damski/8019978119
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Wants you http://www.flickr.com/photos/shutter/105497713/
PETER KOFLER, CODE-COP.ORG FANATIC ABOUT CODE QUALITY