Baby Steps TDD

Approaches

Softwerkskammer Meetup Munich

@codecentric

09.04.2015

David Völkel

Agenda

● Pizza

● Theory

● Coding Kata

● Another beer

Baby Steps

● Who knows the notion?

● 2011 Kent Beck‘s

Responsive Design

● 2013 Adi Bolboaca

Taking Baby Steps

● 2014 Seb Rose & …

Diamond Kata

● [2014 Mikado Method]

How I stumbled upon…

Leap

change 1

Initial code state

change 2

state 1

state 2

…

change n

target code state

● slow feedback

● high risk ● exponential complexity

● problems hard to find

Stepping Stone

change 1

Initial state

change 2

state 1

state 2

…

change n

target state

get green asap ● commit on green

● revert to green

+

Stepping Stone

change 1

Initial state

change 2

state 1

state 2

…

change n

target state

+ fast feedback

+ less risk

- a bit more effort

"Taking Baby Steps“

Kata Contraints (Adi Bolboaca, Erik Talboom)

● Write Feature ● Test

● Implement

● Refactoring

2 min.

2 min.

red?

green?

git reset --hard

git commit

The “Diamond Kata“

A => A B => _A_

B_B

_A_

C => __A__

_B_B_

C___C

_B_B_

__A__

Parallel

● Old and new version

parallel at the same time

● Switch one usage at a time

old create

new

delete old

old not used

anymore

My too big Feature

Simplification

baby feature

Layer 1

Layer 2

integrated test against vertical slice

My too big Feature

Simplification

baby feature

Layer 1

Layer 2

Narrow focus of test

C => __A__

_B_B_

C___C

_B_B_

__A__

C => __A__

Outside-In TDD

Feature

Layer 1

Layer 2

Unit test

Mocks

Component

Feature

Layer 1

Component

Helper Class vs. Method?

Unit test bottom up / inside-out

On-Site TDD

• Temporary assertions in production code

• Delete afterwards

• Even quicker: a REPL

public String diamond(String s) { if (s.equals("A")) { return s; } else { assertEquals("A", predecessor(s)); return (predecessor(s) + s); } }

Test-Recycling

• Start with simple test

• Subsequent rewrites of the

same tests

B => AB

B => ABB

B => A\nBB\n

Let‘s code the “Diamond Kata“!

Contraints "Taking Baby Steps“

● Write Feature ● Test

● Implement

● Refactoring

● [Don‘t talk]

A => A B => _A_

B_B

_A_

C => __A__

_B_B_

C___C

_B_B_

__A__

2 min.

2 min.

red?

green?

git reset --hard

git commit

Retrospective

Images

THOR

https://commons.wikimedia.org/wiki/File:Parkour_leap_of_faith.j

pg?uselang=de

Seattle Municipal Archives

https://commons.wikimedia.org/wiki/File:Kids_at_Kubota_Garde

n_2003.jpg

License

Creative Commons Attribution-ShareAlike 3.0

https://creativecommons.org/licenses/by-sa/3.0/de/