Agile Programming 9 OCTOBER 2013

History

1960’s  60’s  “Cowboys” wrote software anyway that they could  Difference between best programmers and worst as high as 28:1 (many sources)  Start of the “software crisis”  1968  Edsger Dijkstra, “GOTO Statement Considered Harmful” (CACM)GOTO Statement Considered Harmful  Recognition that rules can improve the average programmer

Structuring Software Development  Few rules helped immensely  Good rules and practices developed over the 70’s and 80’s  If a few rules are good, more are better…  Late 80’s, major focus on process as a key to quality  ISO 9000 (first published 1987) ISO 9000  Malcolm Baldrige National Quality Award (just celebrated 25 th anniversary) Malcolm Baldrige National Quality Award

Why not apply to software development?  Companies started codifying their practices  Large documents and people to manage them  Rise of the project manager  “Honored in the breach”  More large projects and more late or failed projects  1995 Standish Group Study 1995 Standish Group Study  Jerry Saltzer SOSP 1999 Jerry Saltzer SOSP 1999

Agile Methodologies: Backlash

Agile Methodologies  Keep only those rules and processes that help  Antidote to bureaucracy  License to hack  Key characteristics  Adaptive  People-oriented

Agile Manifesto  February 2001  Representatives from Extreme Programming SCRUM DSDMAdaptive Software Development CrystalFeature-Driven Development Pragmatic Programming

SCRUM WITH ACKNOWLEDGEMENT TO MIKE COHN FROM MOUNTAIN GOAT SOFTWARE, LLC

We’re losing the relay race Hirotaka Takeuchi and Ikujiro Nonaka, “The New New Product Development Game”, Harvard Business Review, January “The… ‘relay race’ approach to product development…may conflict with the goals of maximum speed and flexibility. Instead a holistic or ‘rugby’ approach—where a team tries to go the distance as a unit, passing the ball back and forth—may better serve today’s competitive requirements.”

Scrum is an agile process that allows us to focus on delivering the highest business value in the shortest time. It allows us to rapidly and repeatedly inspect actual working software (every two weeks to one month). The business sets the priorities. Teams self-organize to determine the best way to deliver the highest priority features. Every two weeks to a month anyone can see real working software and decide to release it as is or continue to enhance it for another sprint. Scrum in 100 words

Characteristics  Self-organizing teams  Product progresses in a series of month-long “sprints”  Requirements captured in “product backlog”  No specific engineering practices prescribed  Uses generative rules to create an agile environment for delivering projects

The Process ©

Sprints  Scrum projects make progress in a series of “sprints”  Typical duration is 2–4 weeks or a calendar month at most  A constant duration leads to a better rhythm  Product is designed, coded, and tested during the sprint

Sequential vs. overlapping development Source: “The New New Product Development Game” by Takeuchi and Nonaka. Harvard Business Review, January Rather than doing all of one thing at a time......Scrum teams do a little of everything all the time RequirementsDesignCodeTest

No changes during a sprint Plan sprint durations around how long you can commit to keeping change out of the sprint Change

Scrum framework Product owner ScrumMaster Team Roles Sprint planning Sprint review Sprint retrospective Daily scrum meeting Ceremonies Product backlog Sprint backlog Burndown charts Artifacts

The team  Typically 5-9 people  Cross-functional: Programmers, testers, user experience designers, …  M embers should be full-time May be exceptions (e.g., database administrator )

Sprint planning meeting Sprint prioritization Analyze and evaluate product backlog Select sprint goal Sprint planning Decide how to achieve sprint goal (design) Create sprint backlog (tasks) from product backlog items (user stories / features) Estimate sprint backlog in hours Sprint goal Sprint goal Sprint backlog Sprint backlog Business conditions Team capacity Product backlog Technology Current product

Sprint planning  Team selects items from product backlog they can commit to  Sprint backlog is created  Tasks are identified and each is estimated (1-16 hours)  Collaboratively, not done alone by the ScrumMaster  High-level design is considered As a vacation planner, I want to see photos of the hotels. Code the middle tier (8 hours) Code the user interface (4) Write test fixtures (4) Code the foo class (6) Update performance tests (4)

The daily scrum  Daily  15-minutes  Stand-up  Not for problem solving  Whole world is invited  Only team members, Scrum Master, product owner talk  Helps avoid other unnecessary meetings

Everyone answers 3 questions  not status for the ScrumMaster  commitments in front of peers What did you do yesterday? 1 1 What will you do today? 2 2 Is anything in your way? 3 3

A sample product backlog Backlog itemEstimate Allow a guest to make a reservation3 As a guest, I want to cancel a reservation. 5 As a guest, I want to change the dates of a reservation. 3 As a hotel employee, I can run RevPAR reports (revenue-per-available-room) 8 Improve exception handling

Hours MonTueWedThuFri Tasks Code the user interface Code the middle tier Test the middle tier Write online help Mon Tues Wed Thur Fri

Scaling through the Scrum of scrums

Extreme Programming

 Complete development process  First code drop 2-3 weeks after start (what is the start?)  Customer part of the development team  Iterative development to the max  Derive requirements with customer through hands-on experimentation  Agile methodology

XP Bills of Rights  Developer has a right to  Clear requirements and priorities  Determine how long a requirement will take  Revise estimates  Always produce quality code

XP Bills of Rights  Customer has a right to  An overall plan  See progress in a running system  Change requirements and priorities  Be informed of changes to schedule and have input as to how to adapt  Cancel in the middle and still have something to show for the investment

XP Value System  Communication  Focus on people, not documentation  Simplicity  Of process and code  Feedback  Mechanism to make useful progress  Courage  To trust in people  (Bollinger: what you would like to know about software that your life depended on)

Extreme Programming Flowchart

User Stories  Use cases  Written by customer  Used for planning  Developers estimate by story  Stories basis for iteration  Used to build acceptance tests  Remember that correctness equals meeting requirements

System Metaphor  Initial system design

Spikes  Technology explorations  Focus on high risk items  Typically considered throw-away code  If not, needs to be agreed to by the whole team

Release Planning  Each iteration has its own plan  Function OR date (other is adjusted accordingly) (Recall 4 variables: function, date, resources, quality)  Planning adapts as the project progresses  Measure project velocity Number of user stories and tasks completed  Next iteration looks at planned vs. actual time Allowed to plan last iteration’s number for this iteration

Iteration  Scope: all parts of the system  Only add functions needed for current user stories  Recommendation: 3 weeks  Moving people around  Backup and training  Code is owned by the whole team  Pair programming  Re-factoring

Pair Programming  Two people working at a single computer  Built-in backup and inspections  Collaboration builds better code  Mechanical model  One drives, the other talks  Keyboard slides between the two  Logical model  One tactical, the other strategic  Both think about the full spectrum but bring different perspectives

Pair Programming Experiments  Typical numbers show the total manpower consumed not very different  Numbers range, but no more than ¼ additional manpower  Implication: actual time is reduced  Improved satisfaction also improves productivity  Williams et al, “Strengthening the Case for Pair-Programming”Strengthening the Case for Pair-Programming

Refactoring  Each iteration adds just the function needed  If you continue to add new functions every two weeks, code can get messy  Refactoring is the cleaning up of the code at the end of the iteration  Critical to maintaining quality code  (Also applies to the design)  Difference between refactoring & rewriting?

Feedback Loops

The Rules of Extreme Programming  Planning  Managing  Designing  Coding  Testing

When to Use XP  Types of projects  High risk  Poorly understood requirements  Team  Small size: 2 to 12  Needs to include customer  Automated testing  Timing issue

What Makes a Project XP  Paradigm  see change as the norm, not the exception  optimize for change  Values  communication, simplicity, feedback, and courage  honor in actions  Power sharing  business makes business decisions  development makes technical decisions  Distributed responsibility and authority  people make commitments for which they are accountable  Optimizing process  aware of process and whether it is working  experiment to fix  acculturate new team members Ward Cunningham, Ron Jeffries, Martin Fowler, Kent Beck

NOT everyone loves XP