Slide of the T.D.D. Coding Dojo (programming language neutral version) T.D.D. Dojo Agenda (3 hours): 05' Welcome and Dojo rules. 15' T.D.D. in a very small nutshell (slides) 05' Q&A 20' TDD Sempai demo (I will show how to use TDD to solve a simple kata) 10' Choose the kata 25' Kata first round 05' break 25' Kata second round 05' break 25' Kata third round 05' break 30' Lesson learned: code sharing

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Test Driven Development Dojo
A safe way to be introduced to a powerful way of programming
!
!
Roberto Bettazzoni

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About me
Agile Coach
eXtreme Programming Trainer
!
>30 years of coding (and still proudly counting)
!
roberto.bettazzoni@agile42.com
linkedin.com/in/robertobettazzoni
@bettazzoni
Roberto Bettazzoni

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T.D.D. Coder Dojo Agenda
• TDD in a very small nutshell
• TDD Sempai demo
• For each Kata (35 min.)
‣ Choose the Kata
‣ execute
‣ break (5 min.)
‣ StandUp
道場
型

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Test Driven Development

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Test-Driven Development as Formula
TDD = ( Test First
+ Unit Testing
+ Refactoring )
* Baby Steps

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Test First

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Test First Programming
!
“Write a failing automated test before
changing any code.”
!
Kent Beck, Extreme Programming Explained 2nd Ed. 2004

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Unit Test

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unit test
Method to verify isolated units of code

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unit test
user
code
Acceptance Criteria test
Functional test
Unit test

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unit test
Method to verify isolated units of code

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unit test
Method to verify isolated units of code

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unit test
assert condition

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unit test
Method to verify isolated units of code

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Test Isolation
B
D
C
A

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Test Isolation
Run 4 tests: A, B, C, D
B
D
C
A

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Test Isolation
B
D
C
A

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Test Isolation
Run 3 tests: A, B, D
B
D
A

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Test Isolation
Run 3 tests: D, A, B
B
D
A

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unit test library
test()

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unit test library
setUp() - test() - tearDown()

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unit test
Method to verify isolated units of code

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unit test - What is a unit of code?
Classes
Methods
Functions
Blocks of code

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Code Isolation (or Unit Isolation)
B
D
C
A

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Code Isolation (or Unit Isolation)
B
D
C
A

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Code Refactoring

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Refactoring
Changing existing code
without changing its external behavior

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Refactoring
Make your code better
without changing its external behavior

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Three Principles to Write Good Code
1. Find good names
2. Remove duplications
3. There is no third principle

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Refactoring. The Sensei Words
Any fool can write code that a
computer can understand.
Good programmers write code that
humans can understand
Martin Fowler, Refactoring: Improving the Design of Existing Code, 1999 pag. 15

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Baby Steps

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Baby steps.
… proceed iteratively in baby steps —
the shortest step that can be
appreciated in the right direction
Kent Beck, Extreme Programming Explained 2nd Ed. 2004

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The TDD process
Unit tests suite pass
unit testa unit test
Write a unit test
Write the code
Refactor the code
Refactor the tests
Unit test
pass
Unit test fails

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The TDD process from the Functional Tests
Add a functional test
Run the test &
check failure
Run all functional
tests see all pass
!
Refactor
the
Design

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Welcome to the coding dojo

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dojo
道場(place of the way)

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kata
型(form)

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Dojo Kun (the dojo rules)
At the Dojo one can’t discuss a form without code, and
one can’t show code without tests. It is a design training
place, where it is acknowledged that “the code is the
design” and that code without tests simply doesn’t exist.
Emily Bache, The Coding Dojo Handbook, 2012
(translated from Christophe Thibaut, Laurent Bossavit’s blog, 2005)
You are here to practice, not to build something
No output is required, neither logging or tracing activities
Every aspect of the kata (design, UI …) is in your hands

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Sempai Demo
Let’s start
the Sempai TDD Demo

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Coding Dojo retrospective

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TDD
ALL CODE IS GUILTY
UNTIL PROVEN INNOCENT

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Food for thoughts