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Agile and XP Development

Learn about the principles, process, and practices of Agile and Extreme Programming (XP) development methodologies and how they prioritize individuals, working software, customer collaboration, and adaptability.

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Agile and XP Development

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  1. Agile and XP Development Dan Fleck 2008 Coming up: What is Agile?

  2. What is Agile? • Software development practice aimed at: • 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. - Excerpt from The Agile Manifesto Coming up: What is Agile?

  3. What is Agile? • A classification of methodologies that adhere to the agile principles • Developed at a conference in Utah in 2000 • Agile Manifesto (agilemanifesto.org) documentation Coming up: An Agile Process

  4. An Agile Process • Is driven by customer descriptions of what is required (scenarios) • Recognizes that plans are short-lived • Develops software iteratively with a heavy emphasis on construction activities • Delivers multiple ‘software increments’ • Adapts as changes occur Coming up: eXtreme Programming (XP)

  5. eXtreme Programming (XP) • Predates Agile • XP was created by Kent Beck at DaimlerChrysler in 1996 • Kent Beck attended the conference in Utah, 2000. • Is probably the best-known and most complete “agile-method” so extreme he never smiles?!? Coming up: XP Fundamentals

  6. XP Fundamentals • Take the good things we do and turn them up to 10! • Simplicity • Communication • Feedback • Courage Coming up: XP Practices

  7. XP Practices • The Planning Game • Small Releases • Metaphor • On-site Customer • Simple Design • Pair Programming • Test-Driven Development • Refactoring • Continuous Integration • Collective Ownership • Coding Standards • Sustainable Pace Coming up: The Planning Game

  8. The Planning Game • Distinguish between business people’s decisions and developer’s decisions • Short iterations (1-2 weeks) • Each iteration satisfies a number of user-stories • Total time for user stories cannot exceed previous iteration’s user story time • Velocity is a measure of the number of stories finished during an iteration. Coming up: Planning Game

  9. Planning Game Split a Story (Customer) Sort stories by value (Customer) “too big” Estimate a story (Developer) Write a Story (Customer) Declare velocity (Developer) “don’t know how” Choose scope (Customer) Spike a Story (Developer) Planning Exploration Coming up: XP - User Stories

  10. XP - User Stories • Similar purpose as use cases • Written by customers • Estimated by developers • Replaces large requirements documents • Represents anything that is “progress” to the customer • Examples: • Students can purchase monthly parking passes online. • Parking passes can be paid via credit cards. • Parking passes can be paid via PayPal • Professors can input student marks. • Students can obtain their current seminar schedule.･Students can order official transcripts. Coming up: The Whole Team

  11. The Whole Team • Communication is key! • Developers, business analysts, QA, project management, customers, etc… all work in one room • Maximizes collaboration Coming up: Small Releases

  12. Small Releases • Systems released to production (or pre-production) very frequently (2-3 months maximum, 1 month is better!) • Much easier to plan next month than the next 6 months Coming up: Continuous Integration

  13. Continuous Integration • The whole system is built and tested several times a day • Automated testing is required (see TDD later) Coming up: System Metaphor

  14. System Metaphor • Establishes common vocabulary for the system • Consistent naming of classes and methods • Names should be easy to learn and relate to Coming up: Example System Metaphor

  15. Example System Metaphor • Examples: Shared blackboard • An Expert puts a Problem on the Board. • There are a number of Experts sitting around: when anyone sees a problem they can solve (or know how to break into easier sub-problems), they do so. • There's a protocol that defines, "Who gets the chalk next?" and "When are we done?" • This metaphor suggests a few potential problems: • experts have different skills, and they may not necessarily agree on how to solve a particular problem. • The chalkboard may become a scarce resource. • The most knowledgeable person may find they're doing all the work. • We may have "experts" who aren't as good as they think they are. Coming up: Sustainable Pace

  16. Sustainable Pace • Coding is a marathon, not a sprint. • Team works 40 hours a week - MAXIMUM! • Tired people aren’t productive Coming up: Pair Programming

  17. Pair Programming • All code is written in pairs • One developer writes code while the other thinks about the code • Is the overall system going to work • Are there better ways of doing this • What test cases still don’t work • Pairs switch roles frequently (every two hours or so) Coming up: Collective Ownership

  18. Collective Ownership • No individual owns any piece of the software. All pieces may be worked on by any team member • Coding Standard - All team members must abide by a coding standard Coming up: Test Driven Development (TDD)

  19. Test Driven Development (TDD) • Write automated unit tests FIRST • Tests must run and fail before code is written • Code then written until unit tests pass • Coding must STOP when unit tests pass (no extra features/functions) • No previously working unit tests can fail Coming up: Refactoring

  20. Refactoring • All code is continuously reviewed and cleaned. Working code is not enough -- must be clean! • Simple Design - the simplest working design that satisfies the task at hand is used. More complex and general designs may become useful, but not now so we don’t use them! Coming up: XP Project People

  21. XP Project People • Customer • Developers • Project Manager • Tracker • Coach Coming up: Tracker

  22. Tracker • Coach • Watches everything • Responsible for the process (keep it extreme!) • Helps with anything else needed… but stay back to let the team be self-reliant! • Tracker • Tracks release plan • Tracks iteration plan • Tracks acceptance tests (passed/failed) Coming up: When not to use XP

  23. When not to use XP • Customer requires a big specification • Large teams > 100 -- no way! Approx 15 people max. • If your solution requires you to create complex solutions for future problems (exponential cost curve) • When you can’t get feedback immediately (space shuttle?) • When you can’t get people physically close together (same room) Coming up: Summary

  24. Summary • eXtreme Programming is a set of practices that conform to Agile principles • Xp is one of many Agile methods: DSDM, Crystal, FDD, SCRUM, and others… • These processes are a logical next step from the older “prescriptive” or “heavyweight” processes Coming up: References

  25. References • These references were used to create these slides: • http://xp123.com/xplor/xp0004/ • http://www.objectmentor.com/omSolutions/agile_xp_differences.html • Beck K., Extreme Programming Explained, 2000 • Pressman R., Software Engineering: A Practitioner’s Approach, 6/e, 2005 Coming up: References

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