Test Driven Design - Speaker Deck

Slide 1

Slide 1 text

TEST DRIVEN DESIGN LEMi ORHAN ERGiN software craftsman @ acm

Slide 2

Slide 2 text

LEMi ORHAN ERGiN agile software craftsman @ acm /lemiorhan lemiorhanergin.com @lemiorhan managing partner at acm developing since 2001 worked at Sony and eBay/GittiGidiyor consultant, architect, trainer, developer founder of Software Craftsmanship Turkey ex product owner of Agile Turkey Summit meetup.scturkey.org summit.agileturkey.org

Slide 3

Slide 3 text

Jack W. Reeves The C++ Journal Vol. 2, No. 2. 1992 http://user.it.uu.se/~carle/softcraft/notes/Reeve_SourceCodeIsTheDesign.pdf What is So!ware Design?

Slide 4

Slide 4 text

Source code is the real so!ware design Designing so!ware is an exercise in managing complexity Jack W. Reeves What is Software Design? The C++ Journal Vol. 2, No. 2. 1992 http://user.it.uu.se/~carle/softcraft/notes/Reeve_SourceCodeIsTheDesign.pdf

Slide 5

Slide 5 text

The so!ware design is not complete until it has been coded and tested Testing is part of the process of refining the design Jack W. Reeves What is Software Design? The C++ Journal Vol. 2, No. 2. 1992 http://user.it.uu.se/~carle/softcraft/notes/Reeve_SourceCodeIsTheDesign.pdf

Slide 6

Slide 6 text

Programming Source Code SOFTWARE DESIGN Test and Verification

Slide 7

Slide 7 text

The very first value of so!ware is… Robert C. Martin Author of Clean Code and Clean Coder Owner of cleancoders.com training site

Slide 8

Slide 8 text

The very first value of so!ware is to tolerate and facilitate on-going changes Robert C. Martin Author of Clean Code and Clean Coder Owner of cleancoders.com training site

Slide 9

Slide 9 text

Each city has to be renewed in order to meet the needs of its populace. So!ware-intensive systems are like that. Grady Booch Developed UML Wrote foreword to “Design Patterns” and “Technical Debt” books Istanbul, Turkey Credit: European Space Imaging

Slide 10

Slide 10 text

Programming Source Code SOFTWARE DESIGN Refactoring Test and Verification

Slide 11

Slide 11 text

Everything is part of the design process Jack W. Reeves What is Software Design? The C++ Journal Vol. 2, No. 2. 1992 http://user.it.uu.se/~carle/softcraft/notes/Reeve_SourceCodeIsTheDesign.pdf

Slide 12

Slide 12 text

but… we develop without driving the design

Slide 13

Slide 13 text

nebula concepts and terminology trigger ideas about the design what we really do in general…

Slide 14

Slide 14 text

proto-star initial classes containing the logic simple structure, basic domain model and behaviors

Slide 15

Slide 15 text

brown dwarf basic dependencies, works as we expect utility classes start to occur

Slide 16

Slide 16 text

main sequence star needless complexity starts, a lot of inter-dependencies manual testing starts to take longer time than usual

Slide 17

Slide 17 text

hard to add new features too much debugging too many workarounds too complex to know every ﬂow red giant

Slide 18

Slide 18 text

blue-white super giant single change aﬀects many areas, no reuse - duplication hell, fragile system - unstable prod scary refactoring, silos occur

Slide 19

Slide 19 text

red super giant huge classes, tons of workarounds, no new features, maintenance mode rules, basic implementations take weeks, no one knows how overall system works, rollbacks a!er deployments, architect saves the company

Slide 20

Slide 20 text

No content

Slide 21

Slide 21 text

No content

Slide 22

Slide 22 text

supernova employee turnovers, frustrated management, blame & fight

Slide 23

Slide 23 text

black hole deadly loop of total rewrite or exit from the market

Slide 24

Slide 24 text

Programming Source Code SOFTWARE DESIGN Refactoring Test and Verification

Slide 25

Slide 25 text

Programming Source Code SOFTWARE DESIGN Refactoring good? Test and Verification

Slide 26

Slide 26 text

COUPLING When readfile() is changed, do you change writeFile() too? It shows how many places we need to change

Slide 27

Slide 27 text

Two elements are loosely coupled if they are not shown in the same diﬀ Kent Beck The creator of extreme programming One of the signatories of the Agile Manifesto Pioneered software design patterns and TDD

Slide 28

Slide 28 text

COHESION Do you search a lot where to change? It shows how easy to find the places we need to change

Slide 29

Slide 29 text

How many files at any one time is still open for edit shows the level of cohesion Nat Pryce Co-Author of Growing Object-Oriented Software Guided by Tests Early adopter of XP

Slide 30

Slide 30 text

Programming Source Code SOFTWARE DESIGN Refactoring Low Coupling Test and Verification High Cohesion

Slide 31

Slide 31 text

Programming Source Code SOFTWARE DESIGN Refactoring is hard and needs discipline! Test and Verification High Cohesion Low Coupling