Essence of Extreme Programming

Agile Software Development: Practices through Values

C Sc 335 Rick Mercer Goal and Outline

Main Goal: – Suggest practices, values, and some process for completing a final project on time that is better than any one could do it in in four times the time. Outline – Distinguish Waterfall (plan driven) from Agile – 11 Practices of quality software development – Four values of Extreme Programming (XP)

2 Waterfall Model

Waterfall was described by 1970 Understood as – finish each phase – don’t proceed till done W. W. Royce criticized this – proposed an iterative approach

3 Became Popular

Management liked phases to easily set deadlines Customers provide all requirements Analysts translate requirements into specification Coders implement the specification Reviews ensure the specification is met Testing is performed by others (QA) Maintenance means modifying as little as possible – old code is good code Change is hard (and costly)

4 Sprial

Dr Barry Boehm proposed a spiral approach

5 Waterfall

It became popular – This process is still is used a lot Craig Larman's book [1] provides proof that waterfall is a terrible way to develop software – In his study, 87% of all projects failed – The waterfall process was the "single largest contributing factor for failure, being cited in 81% of the projects as the number one problem."

[1] Agile and Iterative Development: a Manager's Guide, Addison-Wesley Professional, 2003 6 Extreme Programming (XP)

As of 2009, about 14 years of growth – About 25% of new project are Agile Set of SE practices that produce high-quality software with limited effort Many books, first by Kent Beck: Extreme Programming–Embrace Change, Addison-Wesley, 2000, ISBN 0-201-61641-6 http://www.extremeprogramming.org/ 7 Extreme Programming

XP is – a disciplined approach to software development – code centric: no reckless coding, test-first – successful because it emphasizes customer involvement and promotes team work – not a solution looking for a problem – One of several "agile" (can adapt to change) software development processes http://www.agilealliance.org/

8 Essence of XP

Four variables in software development: – Cost, Time, Quality, Scope (# features) Four Values – Communication, Simplicity, Feedback, Courage Five Principles – Provide feedback, assume simplicity, make incremental changes, embrace change, quality work Practices (or fewer, or more, or subject to change) – Planning game, small releases, simple designs, automated testing, continuous integration, refactoring, pair programming, collective ownership, Continuous Integration, on-site customer, coding standard 9 Cost of change

Waterfall Cost of change

time 10 Cost of the Project

Paraphrasing two companies from Agile When we bid projects, we charge $X for doing it Waterfall and $X/2 for doing it Agile

11 Goal and Outline

12 Practices: Planning Game

The planning game involves story cards, which are short descriptions of a feature – Provide value to customer – Independent of each other – Testable Customer write stories cards and prioritize them Developers estimate how long a story takes

13 Practices: The planning game

Business decisions (customer) – Scope: which “stories” should be developed – Priority of stories (features) – Release dates Technical decisions (developers) – Time estimates for features/stories – Elaborate consequences of business decisions – Team organization and process – Scheduling

14 Practices: Estimation

Based on similar stories from the past Team effort We get good at estimation simply by just doing it Ideal Engineering Time (IET) – could be points Velocity = IET/Calendar Time – we can do 20 points each week – "Customer, which 20 points do you want next week?"

15 Practices: Small Releases

Releases should be as small as possible Should make sense as a whole Put system into production ASAP – Fast feedback Deliver valuable features first Short cycle time – Planning 1-2 months rather than 6-12 months – Or in our case, 2.5 weeks rather than 5 weeks

16 Practices: Simple design

The “right” design – Runs all tests – No code duplication, No code duplication – Fewest possible classes – Short methods – Fulfills all current business requirements Design for today not the future – But design so the system can change

17 Practices: Testing

Software should be tested, but it is often spotty or overlooked Automatic testing (JUnit, for example) help us know that a feature works and it will work after refactoring, additional code, and other changes Provides confidence in the program

18 Testing

Write tests at the same time as production code – Unit tests  developer – Feature/acceptance tests  customer Don't need a test for every method Testing can be used to drive development and design of code Allows for regression testing – Do changes break previously working code

19 SIM/SQS http://www.simgroup.com/Consultancy/regression.html

Regression Testing – re-testing of a previously tested program following modification to ensure that faults have not been introduced or uncovered as a result of changes. – Regression tests are designed for repeatability, and are often used when testing a second or later version of the system under test. – Regression testing can be carried out on all applications, including e-Commerce and web-based systems .

20 Testing

Strong emphasis on regression testing – Unit tests need to execute all the time Unit tests pass 100% Acceptance tests (we haven't seen these) show progress on which user stories are working Other testing frameworks include – JMeter, HttpUnit, JProbe, OptimizeIt, CPPUnit

21 Can't unit test always

Won’t have unit tests for – GUIS: There are testing frameworks to simulate and test user interaction, but not this course – Network, use visual inspection while running – Randomness: Some strategies might have some randomness, which can be hard to work with

22 Practices: Refactoring

Restructure code without changing the functionality Goal: Keep design simple – Change bad design when you find it – Remove dead code Examples at Martin Fowler's Web site:

http://www.refactoring.com/ see online catalog

23 Practices: Pair programming

Write production code with 2 people on one machine – Person 1: Implements the method – Person 2: Thinks strategically about potential improvements, test cases, issues Pairs change all the time. Has advantages such as – No single expert on any part of the system – Continuous code reviews, fewer defects – Cheaper in the long run, and more fun – Can you form a team of 4 and have everyone see all code? Problems: – Not all people like it – Pairs need to be able to work together 24 Practices: Collective ownership

All code can be changed by anybody on the team Everybody is required to improve any portion of bad code s/he sees Everyone has responsibility for the system Individual code ownership tends to create experts

25 Practices: Continuous integration

Integration happens after a few hours of development Checkout build with your changes, Make sure all tests pass (green bar) In case of errors: – Do not put changes into the build – Fix problems Checkin the system to the common repository Repeat We will use CVS to store your code

26 Continuous Integration

Find problems early Can see if a change breaks the system more quickly -- while you remember the details Small increments

27 Practices: Coding standards

Coding Standard – Naming conventions and style – Least amount of work possible: Code should exist once and only once Team has to adopt a coding standard – Makes it easier to understand other people’s code – Avoids code changes because of syntactic preferences

28 Practices: On-site customer

Many software projects fail because they do not deliver software that meets business needs Real customer has to be part of the team – Defines business needs – Answers questions and resolves issues – Prioritizes features

29 Outline

– Process considerations adapted from Scrum 30 Values: Communication

Communication – Customer centric (write "Stories") – Pair programming – Task estimation – Iteration planning • What to do in the next time period • May be weekly goals – Design sessions 31 Values: Simplicity

Simplicity – Choose the simplest thing that will work – Choose the simplest design, technology, algorithm, technique

32 Values: Feedback

Feedback very important – Small Iterations – Frequent deliveries – Pair programming – Constant code review – Continuous integration (add often to the build) – automated unit tests (JUnit, for example)

33 Values: Feedback

Compiler feedback: seconds Pair programming feedback: half minutes Unit test feedback: few minutes Acceptance testing: half hours – Customers write these, no can do in 335 Customer feedback: daily (or several times/week in our case) Iteration feedback: weekly

FeedBack? 34 Manifesto for Agile Software Development Agile Manifesto

We are uncovering better ways of developing software by doing it and helping others do it. Through this work we have come to value: Individuals and interactions over processes and tools Working software over comprehensive documentation Customer collaboration over contract negotiation Responding to change over following a plan

That is, while there is value in the items on the right, we value the items on the left more.

35 Outline

SLs and Rick are the customers – Projects still TBD – Will choose teams/projects next Thursday 28-Oct As customers, we reserve the right to change requirements :-)