Agile Software Development

Agile Software Development

• Rapid development and delivery have become the most important requirements for software systems
• Businesses operate at a fast pace leading to quickly changing requirements
• Software must evolve quickly to reflect changing business needs
• Agile development methods emerged in the late 1990s to reduce delivery time for working software

Agile Development

• Program specification, design, and implementation are interleaved
• The system grows through versions with stakeholder input in version specification and evaluation
• Continuous deployment and frequent releases are integral
• New versions are frequently delivered for evaluation, typically with daily or weekly builds
• Automated testing tools provide Extensive tool support
• Testing is performed on versions before integration
• Focus is on working code, minimizing documentation

Plan-Driven Development

• Software engineering relies on separate development stages
• Each stage has planned outputs determined in advance
• Not necessarily a waterfall model, it can also be plan-driven and incremental
• Iteration occurs within activities

Agile Development

• Relies on interweaving Specification, design, implementation, and testing
• Outputs are determined through negotiation during development

Agile Methods

• Agile methods were created due to dissatisfaction with the overheads of software design methods in the 1980s and 1990s
• Focuses on code over design
• Stresses an iterative approach and delivers working software quickly
• Software intended to rapidly evolve to meet changing requirements
• Aims to reduce overhead by reducing documentation
• Quickly adapt to feedback and changing requirements without rework

Agile Manifesto Values

• Prioritizes Individuals and interactions over processes and tools
• Values Working software over documentation
• Supports Customer collaboration over contract negotiation
• Is centered around Responding to change over following a plan

Agile Method Principles

• Customer involvement: Customers remain closely involved through the development process to provide input and evaluate iterations of the system
• Incremental delivery: Deliveries are developed incrementally, including customer-specified requirements in each release
• People not process: Skill is valued on the development team, and developers are trusted to self-organize ways of working
• Embrace change: The system is designed to accommodate change
• Focus on simplicity: Efforts are made to remove system complexity

Agile Method Applicability

• Most software products and apps are built using an agile approach
• Best used in product development for small to medium-sized product sales
• Suited for custom system development with clear customer commitment and limited external rules

Extreme Programming (XP)

• It is an influential agile method from the late 1990s
• Utilizes iterative development
• Consists of builds produced frequently (multiple times daily)
• Increments are delivered to customers bi-weekly
• Builds must pass all tests

Extreme Programming Practices

• Incremental planning: Requirements are recorded on story cards, stories are prioritized, and broken into development tasks
• Small releases: A minimal set of functionality providing business value is released frequently with incremental additions
• Simple designs: Designs are carried out to meet current requirements
• Test-first development: Automated unit tests confirm functionality before implementation
• Refactoring: Code is improved continuously for simplicity and maintainability
• Pair programming: Developers working in pairs, provide continual feedback, checking each other's work
• Collective ownership: Developers work on all the system to ensure all developers feel responsible for all of the code
• Sustainable pace: Overtime is limited to maintain productivity
• On-site customer: A customer representative is available full-time for the XP team to implement and bring system requirements

XP Values

• Communication should be Frequent
• Simplicity involves the easiest path to a goal
• Feedback leads to continuous learning
• Courage to address issues
• Mutual Respect among those involved

XP and Agile Principles

• Incremental development is supported through system releases
• Customer involvement includes full-time engagement with the team
• People are prioritized over process: pair programming, collective ownership, and avoidance of long hours
• Change is supported with regular system releases
• Simplicity is maintained with constant refactoring

Influential XP Practices

• It has a technical focus that isn't easy to integrate into management
• Agile development uses various practices from XP, the method isn't widely used as defined
• Key practices for agile development include: user stories for specification, refactoring, test-first development, and pair programming

XP - Expressed Requirements

• User stories or scenarios are used to explain user requirements
• Requirements are written on cards
• The team organizes them into implementation tasks, and estimates associated costs and schedules
• Stories are assigned to releases based on priorities and schedule

Refactoring

• The wisdom within software engineering is to design for change
• It spends a considerable amount of anticipating any changes as this reduces any future costs
• XP maintains that that changes cannot be reliably anticipated
• It proposes constant code improvement (refactoring) to make changes easier for implementation.

Refactoring Practices

• Includes reorganizing a class hierarchy to eliminate duplicate code
• A practice that includes tidying up and renaming attributes and methods
• Can involve replacing inline code with calls to methods included in a program library

Test-Driven Development

• Involves writing tests before code to clarify and define requirements
• Tests are written as executable programs that verify proper execution
• It relies on testing framework, such as JUnit for execution
• Tests from new or previous versions are used to ensure that new functionality doesn't introduce errors

Customer Roles in Testing

• Customers help create acceptance tests for included stories within system releases
• With the team customers write tests as development proceeds
• With new codes, what the customer requires are validated

Test Case Elements

• Input represents the value for a single dose
• Tests measure output with parameters that are too high, too low, or within range

Test Automation

• Involves writing tests as executable components before task implementation
• Testing components simulate the submission of test input to ensure the result meets output specifications
• Automated test frameworks simplify writing and executing tests

Pair Programming

• Programmers work in pairs while developing code
• It develops shared ownership and spreads knowledge through those on the team
• This is an informal review process because multiple people view each line of code
• Encourages code refactoring

Aims of Pair Programming

• Programmers work together at the same computer to develop software
• Pairs are created dynamically
• Working with others promotes knowledge sharing and reduces risks if team members leave
• Increases working efficiency within the team

Project Management

• Project managers manage projects, delivering software on time and within budget
• They select and prioritize key functions to implement in timely builds
• This differs from standard project management where managers create extensive plans
• Agile requires a different approach adapted to using agile's incremental development and practices

Scrum

• It is an agile method that focuses on managing iterative development
• It consists of planning, sprint cycles, and project closure to develop the system

Scrum Terminology

• Development team: A self-organized unit of developers, usually no more than 7 people
• Sprint: An increment that can be shipped during software development
• Product backlog: A list that provides the tasks must tackle by the Scrum team
• Product owner: Responsible to identify product requirements, prioritize them for new releases, and constantly review the backlog to meet any needs

Sprint Review

• The Scrum team meets daily to check project progress and prioritize tasks. It should be a short face-to-face meeting for the complete team.
• The ScrumMaster ensures the process is followed and is responsible for guiding the team on using scrum
• This process is an iterative development cycle with sprints that are fixed in length
• Estimates are generated on how well a team can do in velocity to provide measurements for progress improvements

Agile Scaling

• Agile methods are successful with local teams
• Improved communication accounts for much of this success
• Changes within larger systems requires scaling up, for multiple teams and locations

Scaling

• Involves the use of agile methods for developing software systems that cannot be developed by a single team
• Can be introduced throughout large organizations
• It's crucial to adopt flexible planning, frequent releases, continuous integration, test development, and good communications

Issues with Agile Methods

• Incompatible with legal definitions of work
• Most appropriate for new software but not most modern systems
• It is difficult to perform within distributed teams

Contractual Agile Factors

• Custom systems contracts rely on the specification developed by the customer
• This blocks the mixing of specification with agile norms
• Contracts must allow for a developer's time rather than functionality because no long-term guarantees can be offered