Agile Software Development is a method of software development that works for small projects to provide quick and efficient solution.

1. Chapter 3 Agile software development
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Chapter 3 – Agile Software
Development

2. Topics covered
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 Agile Development
 Extreme Programming (XP) Methodology
 Pair Programming

3. Rapid software development
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 Rapid development and delivery is now often the
most important requirement for software systems
 Businesses operate in a fast –changing requirement and it is
practically impossible to produce a set of stable software
requirements
 Software has to evolve quickly to reflect changing business needs.
 Rapid software development
 Specification, design and implementation are inter-leaved
 System is developed as a series of versions with stakeholders
involved in version evaluation
 User interfaces are often developed using an IDE and graphical
toolset.

4. What is Agile Development?
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 Agile is an emerging software development
methodology
 Programming-centric
 Few rules and practices
 Easy to follow
 Eliminate much of modeling and documentation
tasks – saves time
 Emphasize simple, iterative application development

5. Agile methods
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 Dissatisfaction with the overheads involved in software
design methods of the 1980s and 1990s led to the creation
of agile methods. These methods:
 Focus on the code rather than the design
 Are based on an iterative approach to software development
 Are intended to deliver working software quickly and evolve
quickly to meet changing requirements.
 The aim of agile methods is to reduce overheads in the
software process (e.g. by limiting documentation) and to be
able to respond quickly to changing requirements without
excessive rework.

6. Agile manifesto
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 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.

7. The principles of agile methods
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Principle Description
Customer involvement Customers should be closely involved throughout the
development process. Their role is provide and prioritize new
system requirements and to evaluate the iterations of the
system.
Incremental delivery The software is developed in increments with the customer
specifying the requirements to be included in each increment.
People not process The skills of the development team should be recognized and
exploited. Team members should be left to develop their own
ways of working without prescriptive processes.
Embrace change Expect the system requirements to change and so design the
system to accommodate these changes.
Maintain simplicity Focus on simplicity in both the software being developed and
in the development process. Wherever possible, actively work
to eliminate complexity from the system.

8. Extreme Programming
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 Perhaps the best-known and most widely used agile
method.
 Extreme Programming (XP) takes an ‘extreme’
approach to iterative development.
 New versions may be built several times per day;
 Increments are delivered to customers every 2 weeks;
 All tests must be run for every build and the build is only
accepted if tests run successfully.

9. Extreme Programming (cont.)
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 Extreme Programming is founded on four core
values:
 Communication
 Simplicity
 Feedback
 Courage
 Developers must provide rapid feedback to the end
users on a continuous basis
 XP requires developers to follow the KISS principle

10. Extreme Programming (cont.)
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 Developers must make incremental changes to grow
the system – must embrace change
 Developers must have a quality first mentality
 Three key principles used by XP to create successful
systems:
 Continuous testing
 Coding performed by pairs of developers
 Close interactions with end users

11. Extreme Programming (cont.)
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 XP project begins with user stories that describe
what the system needs to do
 Programmers code in small, simple modules and test
to meet those needs
 Users are required to be available to clear up
questions and issues
 Standards are very important to minimize confusion
 XP projects deliver results sooner than even the RAD
approaches

12. Problems with XP
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 For large projects, applying XP is not easy
 XP is only recommended for small groups of developers—no
more than 10 developers
 Project members need to work well and co-operate as part of a
team
 XP requires a great deal of discipline – otherwise projects will
become unfocused and chaotic
 Maintaining large systems built with XP is difficult – lack of
analysis and design documentation, only code documentation
 On-site customer availability not always possible

13. Testing in XP
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 Testing is central to XP and XP has developed an
approach where the program is tested after every
change has been made.
 XP testing features:
 Test-first development.
 User involvement in test development and validation.
 Automated test harnesses are used to run all component tests
each time that a new release is built.

14. Test-first development
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 Writing tests before code clarifies the requirements
to be implemented.
 Tests are written as programs rather than data so
that they can be executed automatically. The test
includes a check that it has executed correctly.
 Usually relies on a testing framework such as Junit.
 All previous and new tests are run automatically
when new functionality is added, thus checking that
the new functionality has not introduced errors.

15. Pair programming
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 In XP, programmers work in pairs, sitting together to
develop code.
 This helps develop common ownership of code and spreads
knowledge across the team.
 It serves as an informal review process as each line of code
is looked at by more than 1 person.
 It encourages refactoring as the whole team can benefit
from this.
 Measurements suggest that development productivity with
pair programming is similar to that of two people working
independently.

16. Pair programming (cont.)
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 In pair programming, programmers sit together at
the same workstation to develop the software.
 Pairs are created dynamically so that all team
members work with each other during the
development process.
 The sharing of knowledge that happens during pair
programming is very important as it reduces the
overall risks to a project when team members leave.
 Pair programming is not necessarily inefficient and
there is evidence that a pair working together is more
efficient than 2 programmers working separately.

17. Advantages of pair programming
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 It supports the idea of collective ownership and
responsibility for the system.
 Individuals are not held responsible for problems with the
code. Instead, the team has collective responsibility for
resolving these problems.
 It acts as an informal review process because each
line of code is looked at by at least two people.
 It helps support refactoring, which is a process of
software improvement.
 Where pair programming and collective ownership are used,
others benefit immediately from the refactoring so they are
likely to support the process.

18. References
 Cornell University, USA
http://www.cs.cornell.edu/courses/cs501/2000fa/slides.html
 Picture collect from: Ivan Marsic, Rutgers
University
 Ian Sommerville, Software Engineering, 9th
edition, Pearson, 2011
 Roger s. pressman, Software Engineering a
practitioners approach, 7th ed

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