Agile Methods and Extreme Programming

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Agile Methods andExtreme Programming

• CSSE 376, Software Quality Assurance
• Rose-Hulman Institute of Technology
• March 23, 2007

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Outline

1. Origin of Agile Methods
2. Extreme Programming
3. Test First Development

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I. Origin of Agile Methods
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First Cartoon of the Day
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Spectrum of Methods
Source "Get ready for agile methods, with care"
by Barry Boehm, IEEE Computer, January 2002.
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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.

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Some Agile Methods

• ASD - Adaptive Software Development
• Crystal
• FDD - Feature Driven Development
• DSDM - Dynamic Systems Development Method
• Lean Software Development
• Scrum
• XP - eXtreme Programming

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II. Extreme Programming
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Motivation

• Knobs on a control board
• Each knob a practice that works well
• Turn all knobs up to 10

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Learning to Drive

• "Driving is not about getting the car going in
  the right direction.
• Driving is about constantly paying attention,
  making a little correction this way, a little
  correction that way."
• -- Kent Beck, Extreme Programming Explained

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Four Values

• Simplicity
• create the simplest thing that could work
• Communication
• face-to-face, not document-to-face
• Feedback
• lots of tests
• Aggressiveness

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Four Basic Activities

• Coding
• cannot do without it
• Testing
• if it cannot be tested it doesn't exist
• Listening
• to those with domain knowledge
• Designing
• to keep the system from decaying

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Twelve Practices

1. Pair programming
2. Collective ownership
3. Continuous integration
4. 40-hour week
5. On-site customer
6. Coding standards

1. The Planning Game
2. Small releases
3. Metaphor
4. Simple design
5. Testing
6. Refactoring

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Waterfall to XP Evolution
Source "Embracing change with extreme
programming" by Kent Beck,IEEE Computer, October
1999.
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5. Testing

• Any feature without an automated test does not
  exist.
• Programmers need confidence in correct operation
• Customers need confidence in correct operation

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Tools for Testing

• Test harnesses for various programming languages
• Simplify job of creating and running the tests

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Second Cartoon of the Day
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7. Pair Programming

• All code written with 2 people at one machine
• Driver
• thinks about best way to implement
• Passenger
• thinks about viability of whole approach
• thinks of new tests
• thinks of simpler ways

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Workspace
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9. Continuous Integration

• Integrate and test every few hours, at least once
  per day
• All tests must pass
• Easy to tell who broke the code

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III. Test First Development
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Code the Unit Test First

• Makes it easier to write the code
• Translates requirements to specific tasks that
  must be accomplished by code
• Creates tests at moments when they can best be
  defined
• Provides immediate feedback to coding

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Similar to Deming's PDSA Cycle (below)

• Plan Write a test case expressing what you hope
  to accomplish.
• Do Write the code.
• Study Run the test.
• Act If it passes, check the code in and go on.
  If it fails, rerun the cycle. Maybe the code is
  bad or maybe the test is bad.

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Side Effects

• Designing in small steps
• only need to do a little bit at a time
• A sense of unhurriedness
• always know what you are doing and when you are
  done
• Monological thinking
• focus on one thing at a time