Introduction to eXtreme Programming (XP)

1. Introduction to eXtreme Programming (XP) Collaboration in Software Development Process

2. XP overview • A large percentage of software projects fail, due to a variety of problems we will see • Most of these problems are really issues of Design, Learning, and Collaboration in the software process • XP takes innovative approaches to improve Design, Learning, and Collaboration in the software process

3. Traditional Problems, XP solutions • Problem: Improper planning • Not enough planning • Too much planning: planning for situations that will never occur • Solution: XP says to quickly determine the scope of the next (short) development cycle. • Business priorities • Technical feasibility • Keep the plan updated as things change • Result: improved Design

4. Traditional Problems, XP solutions • Problem: Schedules blown at the last minute: • Example: software project where all development is done before integration • Integration takes unexpectedly long • Solution: XP promotes Iterative development: Releases as small as possible • Solution: XP also includes constant integration • Result: managed risk

5. Traditional Problems, XP solutions • Problem: Design doesn’t fit together well because individual designers and implementers all have different ideas • Solution: In XP, a Metaphor, or simple shared story, is created for the entire project • Result: improved Collaboration

6. Traditional Problems, XP solutions • Problem: “Over-engineered” software • Design for situations that will never occur • Complexity causes defects • Solution: Extreme programming promotes maximum simplicity • Implement the bare minimum that is needed now • Add additional complexity as it is needed • Result: improved Design

7. Traditional Problems, XP solutions • Problem: The last few weeks in a 6 month long project is allocated for testing, but testing takes 4 more months instead • Solution: XP requires that programmers write unit tests for all code • All tests must pass before development on new items can continue • Result: improved Design

8. Traditional Problems, XP solutions • Problem: Programmers know about bad sections of code, but do not fix them • They don’t feel like they have time • They are afraid to cause more trouble • Solution: XP makes Refactoring an official part of the development process. • Programmers are empowered to fix problems • Result: improved Design

9. Traditional Problems, XP solutions • Problem: Programmers just code without thinking about the big picture, design problems and bugs result • Solution: XP requires that _all_ production code be written with 2 programmers behind the desk, one typing and one observing • Pairs are “rotated” over time • Result: improved collaboration AND learning

10. Traditional Problems, XP solutions • Problem: One programmer won’t let others work on “his code,” thus nobody else understands it. Then he gets hit by a bus. • Solution: in XP, everyone owns all of the code. Everyone is allowed to work on any part of the system • Result: improved collaboration and learning

11. Traditional Problems, XP solutions • Problem: Programmer works 80 hours per week on a “death march” project trying to get a release out the door, wife leaves him, he quits to become a candle maker in Oregon • Solution: XP requires 40 hour weeks, and never allows overtime 2 weeks in a row • Result: Improved performance of programmers in many ways

12. Traditional Problems, XP solutions • Problem: Customer wants a High Heel shoe, development builds a Combat Boot • Development solves the wrong problem • Solution: XP requires a “real life customer” on every team, ensuring that the project solves the right problems. • Result: improved collaboration (with customer)

13. Traditional Problems, XP solutions • Problem: Every programmer uses the language in different ways, formats their code and declares variables differently • Solution: XP implements coding standards so that a programmer new to a section of code can quickly attack the problem, not the style • Result: improved collaboration

14. Traditional Problems, XP solutions • Problem: A programmer spends hours on a problem that the person in the next cubicle could have answered in 2 minutes • Solution: XP includes daily meetings where each programmer shares what he or she is working on. • This gets difficulties out in the open • Solution: Pair programming helps engineers keep track of what everyone on the team knows best • Result: improved collaboration

15. Senior Developer views of XP • Interviewed 2 • Not a pure XP environment, but rapid development • These developers are familiar with XP • Their names are Scott and Pete

16. Senior Developer views of XP • Planning • Both agreed that a clear “forest” view is necessary – understand the problem to solve • Easier with short iterations • Short iterations • Pete: major construction requires longer iterations, at the risk of schedule predictability • Suggests conservative scheduling for heavy construction phases

17. Senior Developer views of XP • Metaphor • Pete: One person sets the direction for a product • Consider feedback from others • This is a “best practice” in other processes • XP does not do this, more consensus based

18. Senior Developer views of XP • Simplicity • Scott: strike a balance with Flexibility • Pete: believes maximum simplicity can still be flexible • Testing • Pete: unit tests for every line difficult in practice • Acceptance tests equally important

19. Senior Developer views of XP • Refactoring • Both agree that refactoring has been going on for a long time • But making it an official part of the process helps, especially for scheduling • Pair programming • Pete hates pair programming • Feels that a solid engineer can beat any 2 engineers together

20. Senior Developer views of XP • Collective ownership • Pete: Everyone should be familiar with all parts of the system • BUT there should be a “Design Owner” for important sections, to maintain vision in the small • 40 hour week • Both feel this is possible in a stable world • Pete would rather work more some of the time • 40 hours is very arbitrary

21. Senior Developer views of XP • Customer on the team • Pete: Real customers don’t know what they want • Give shallow feedback • The “Vision Keeper” for the product should know enough about the customers to be the “uber user”

22. Strategies in XP Collaboration in Software Development Process

23. XP – Strategies • Traditionalism is skeptical towards change • Paradigm shifts require strategies to tackle… • Planning • Management • Design • Development • Testing

24. XP - Planning Strategy • Goal: maximize value • Game plan: low investment, high return • Actors: developers, managers, clients • Tools: user stories, CRC cards • Actions: explore, commit, steer

25. XP - Management Strategy • Estimate: metrics, *relevance* • Train: actors (programmers) • Track: progress, compatibility • Reorganize: teams, solutions, problem space

26. XP - Design Strategy • Stick to the values! • Simplicity • Low initial investment • Lightweight • Incremental change

27. XP - Design Strategy (cont’d…) Cost of change grows dramatically over time

28. XP - Design Strategy (cont’d…) Cost of change remains cheap over time

29. XP - Development Strategy • Quick iteration • Small releases • Collective ownership • Pair programming • Refactoring • Testing • Continuous integration

30. XP - Testing Strategy } Test suite = Product specs. You pass the tests, you fulfill the specs. • Unit • Acceptance • Parallel • Stress • Monkey !!

31. VCAPS – (Vehicle Cost and Profit System)Ford Motor Company, 1993 • Planning – Changing specs, priorities, regulations… caught up!! • Management – Separated from technical issues. Had a low view of developers’ efficiency. • Design – Mostly centralized, code got UGLY • Leadership and Coaching – Low morale • Integration: 20+ developers, race to the finish, ONE integrator working nights • Testing – Last two months. Bugs had a domino effect.

32. VCAPS – XP to the rescue • Planning – CRC card culture: bigger picture • Management – Integrated. Developers had responsibility and authority. One-week iterations. Upper management worked as before. • PP – caught up more slowly, initial reluctance. Teaching techniques & level of experience. Pairs vs. Trios.

33. VCAPS – XP to … (cont’d) • Integration: small releases nip the problem in the bud. • Testing – smaller sized unit and functional tests: more targeted, easier to automate.

34. VCAPS - Conclusion • 9 out of 12 XP practices embraced. • Threw away old system and started afresh. • Took one year for people to start enjoying. • Management stopped seeing value. Customers still wanted it. Got canned!! • Lessons: • Transition slowly, one practice at a time. • Management must take the lead. • test vigorously, release frequently.

35. Activity Collaboration in Software Development Process

36. Pair Programming Collaboration in Software Development Process

37. Introduction • Two programmers working side by side as stated by Kent Beck in Extreme Programming (XP) in 1996. • Objective is to improve software Quality and reduce Time-to-Market. • Pairs enjoy problem-solving process and outperform individual programmers. • They have greater confidence in their solutions.

38. Pair Jelling • Two programmers jointly produce one artifact. • One partner is the driver and has control of the pencil/mouse/keyboard and is writing the design or code. • The other person continuously and actively observes the work of the driver (watching for defects, thinking alternatives, looking up resources, and considering strategic implications of the work at hand).

39. Pair analysis and Pair design • It is important for the pair to collectively agree on the development direction and strategy outlined during these stages. • “Two brains are better than one” when performing analysis and design. • Significantly decreases the probability of proceeding with a bad design. • Other partner can think more strategically about implications of the design. • Avoid “design tunnel vision”.

40. Pair implementation • One programmer types into the computer while the other is actively engaged in observing, performing a continuous code review. • Efficient form of defect removal: removed right from the start. • Drawback: most programmers prefer to do a thorough review of their individual work and incorporate it into the project.

41. Pair Testing • Is the least critical part of the development cycle, as long as the pair develops the test cases together. • Testing discovers new bugs. Pair testing allows for different points of view on how to test an application, hence finding even more bugs.

42. Good Practices for Pair Programming • Don’t hit your partner: make sure your partner stays focused and on-task. • Put things back where they belong: have confidence but not too much confidence. • Clean up your mess: The “watch over the shoulder” technique epitomizes defect prevention and efficient defect removal.

43. Good Practices for Pair Programming • Don’t take things too seriously: “Ego-less programming” • Say you’re sorry when you hurt somebody while moving furniture: Appropriate workspace layout is critical to the pair success. • Wash your hands of skepticism before you start: develop an expectation of success and greet your collaborative partner.

44. Good Practices for Pair Programming • Flush: Pair programmers will work on something independently, when rejoining your partner review your work done separately. • When you go out into the world, watch out for traffic, hold hands and stick together: your work is done together, do not leave your partner apart. • Be aware of the power of two brains: You remember better, more knowledge and skills.

45. Good Practices for Pair Programming • Take a break from working together every afternoon: experiment new prototypes, deep-concentration, logical thinking is preferred to do it alone. • Live a balanced life – learn some and think some and draw and paint and sing and dance and work every day some.

46. Issues in Pair Programming • How do you create a good pair? • One personality might consume the other. Or two clashing personalities might not get work done. • Programmers tend to split work for more rote, routine and simple coding of a project. • Design review might be best in larger numbers (Design Review Boards). But Design alone is better in small numbers.

47. Issues in Pair Programming • What is a conducive workplace? • Offices and cubicles are regular settings for offices that hinder pair programming. • “Like many kings, some managers use divide-and-conquer tactics to rule their subjects, but programmers need contact with other programmers.” (Weinberg 1998).

48. Issues in Pair Programming • How much time should it occupy in a work day? • Many programmers do not agree how much time they should give for pair programming. • From all-day extreme, to few minutes a day. • Alternative Solutions: “Distributed pair programming” (Baheti, Gehringer, Stotts).

49. Interviews and Results • An experiment in Temple University showed that pair programmers produced 40% more quickly and effectively. Contrary to the notion of managers that believe that it would mean a 100% increase of production time. • 96% stated that they enjoyed their job more than when they programmed alone.

50. Interviews and Results • Design is good in pairs, even better in 3-5 members. But more than that it hinders (never reach to an agreement). • Pair programmers is a positive form of peer pressure. • Simple tasks should be done alone, but by pair design you can identify which tasks need to be done in pairs. • Pairs enjoy their work more because they are more confident in their results.