Agile Development Chapter 3

Agile Development

• The Agile Alliance signed the "Manifesto for Agile Software Development" in 2001, emphasizing customer satisfaction, early delivery, and responding to change.
• Agile software engineering combines a philosophy and development guidelines, focusing on customer satisfaction, small project teams, informal methods, and simplicity.

Key Concepts

• Agile development:
  • Values individuals and interactions over processes and tools
  • Places working software over comprehensive documentation
  • Prioritizes customer collaboration over contract negotiation
  • Responds to change over following a plan
• Agile process models:
  • Adaptive Software Development (ASD)
  • Scrum
  • Dynamic Systems Development Method (DSDM)
  • Crystal
  • Feature Driven Development (FDD)
  • Lean Software Development (LSD)
  • Agile Modeling (AM)
  • Agile Unified Process (AUP)

Agility

• Agility in software engineering:
  • Recognizes the importance of embracing change
  • Involves a team structure and attitude that facilitates communication
  • Emphasizes rapid delivery of operational software
  • De-emphasizes intermediate work products
• Jacobson's view on agility:
  • Change is the primary driver for agility
  • Agility involves recognizing the importance of individuals working in teams

Cost of Change

• Conventional software development: the cost of change increases nonlinearly as a project progresses

• Agile development:

  • Reduces the cost of change by delivering software in increments
  • Enables accommodating changes late in a project without significant cost and time impact
  • Practices like continuous unit testing and pair programming help control change within an increment### Agile Development

• Agile software process addresses key assumptions about software projects:

  • Difficulty in predicting software requirements and customer priorities
  • Interleaved design and construction
  • Unpredictability in analysis, design, construction, and testing

• An agile process must be adaptable and incremental to manage unpredictability

• Adaptation requires customer feedback, which can be facilitated through an operational prototype or incremental development strategy

Agility Principles

• The Agile Alliance defines 12 principles for achieving agility:
  • Satisfy the customer through early and continuous delivery of valuable software
  • Welcome changing requirements, even late in development
  • Deliver working software frequently
  • Business people and developers must work together daily
  • Build projects around motivated individuals
  • Face-to-face conversation is the most efficient method of conveying information
  • Working software is the primary measure of progress
  • Agile processes promote sustainable development
  • Continuous attention to technical excellence and good design enhances agility
  • Simplicity is essential
  • The best architectures, requirements, and designs emerge from self-organizing teams
  • The team reflects on how to become more effective and adjusts its behavior accordingly

The Politics of Agile Development

• There is ongoing debate about the benefits and applicability of agile software development
• Agile development is not a replacement for software engineering, but rather a complementary approach
• The key question is how to achieve agility while meeting customers' needs today and in the long term

Human Factors

• Agile development focuses on the talents and skills of individuals, molding the process to specific people and teams
• The process must be tailored to the needs of the people and team, rather than the other way around
• Key traits for an effective software team include:
  • Competence
  • Common focus
  • Collaboration
  • Decision-making ability
  • Fuzzy problem-solving ability
  • Mutual trust and respect
  • Self-organization

Extreme Programming (XP)

• XP is an agile process that emphasizes communication, simplicity, feedback, courage, and respect

• XP values are used as a driver for specific activities, actions, and tasks

• Communication is facilitated through close collaboration between customers and developers, effective metaphors, continuous feedback, and avoidance of voluminous documentation

• Simplicity is achieved by designing for immediate needs and refactoring later if necessary

• Feedback is derived from the software itself, the customer, and other team members

• Courage (or discipline) is required to adhere to certain XP practices### Agile Development: Extreme Programming (XP)

• Agile teams often argue that designing for the future will save time and effort in the long run, but XP teams must design for today, recognizing that future requirements may change dramatically.

The XP Process

• XP uses an object-oriented approach as its preferred development paradigm.
• The XP process encompasses four framework activities: planning, design, coding, and testing.
• Planning involves listening to the customer, creating user stories, and assigning values and costs to each story.
• The XP team orders the stories to be developed in one of three ways: by implementing all stories immediately, prioritizing high-value stories, or prioritizing riskiest stories.

User Stories

• A user story describes required output, features, and functionality for software to be built.
• Each story is written by the customer and placed on an index card.
• The customer assigns a value (priority) to the story based on the overall business value of the feature or function.

Project Velocity

• Project velocity is the number of customer stories implemented during the first release.
• It helps estimate delivery dates and schedule for subsequent releases and determines whether an overcommitment has been made for all stories across the entire development project.

Design

• XP design follows the KIS (keep it simple) principle.
• A simple design is always preferred over a more complex representation.
• The design provides implementation guidance for a story as it is written, nothing less, nothing more.
• XP recommends the use of CRC cards as an effective mechanism for thinking about the software in an object-oriented context.

Refactoring

• Refactoring is a construction technique that improves the internal structure of a design (or source code) without changing its external functionality or behavior.
• Refactoring is used to control modifications by suggesting small design changes that can radically improve the design.

Coding

• XP recommends that two people work together at one computer workstation to create code for a story, called pair programming.
• Pair programming provides a mechanism for real-time problem solving and real-time quality assurance.
• Once the code is complete, it can be unit-tested immediately, providing instantaneous feedback to the developers.

Testing

• Unit tests are created before coding commences, focusing on an individual software component.
• Unit tests are implemented using a framework that enables them to be automated.
• Acceptance tests, also called customer tests, are specified by the customer and focus on overall system features and functionality.

Industrial XP (IXP)

• IXP is an organic evolution of XP that incorporates six new practices to ensure success for significant projects within a large organization.
• The new practices include readiness assessment, project community, and others.
• IXP differs from the original XP in its greater inclusion of management, its expanded role for customers, and its upgraded technical practices.