Agile Development Techniques and Project Management, Summaries of Commercial Law

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2. Agile & UML

Objects

• Agile

 methods

 development techniques

 project management

• UML

 4+1 view

Agile methods

• 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

this 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.

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.

Agile method applicability

• Product development where a software company is developing a small or medium-sized product for sale.  Virtually all software products and apps are now developed using an agile approach
• Custom system development within an organization, where there is a clear commitment from the customer to become involved in the development process and where there are few external rules and regulations that affect the software.

Agile development techniques

Extreme programming - XP

• A very influential agile method, developed in the late 1990s, that introduced a range of agile development techniques.
• Extreme Programming takes an ‘extreme’ approach to iterative development.  New versions may be built several times per day;  Increments are delivered to customers every 1 - 2 weeks;  All tests must be run for every build and the build is only accepted if tests run successfully.

• Extreme programming practices (a) Principle or practice Description Incremental planning Requirements are recorded on story cards and the stories to be included in a release are determined by the time available and their relative priority. The developers break these stories into development ‘Tasks’. See Figures 3.5 and 3.6. Small releases The minimal useful set of functionality that provides business value is developed first. Releases of the system are frequent and incrementally add functionality to the first release. Simple design Enough design is carried out to meet the current requirements and no more. Test-first development An automated unit test framework is used to write tests for a new piece of functionality before that functionality itself is implemented. Refactoring All developers are expected to refactor the code continuously as soon as possible code improvements are found. This keeps the code simple and maintainable.

• Extreme programming practices (b) Analysis and Design of IS 11 Principle or practice Description Pair programming Developers work in pairs, checking each other’s work and providing the support to always do a good job. Collective ownership The pairs of developers work on all areas of the system, so that no islands of expertise develop and all the developers take responsibility for all of the code. Anyone can change anything. Continuous integration As soon as the work on a task is complete, it is integrated into the whole system. After any such integration, all the unit tests in the system must pass. Sustainable pace Large amounts of overtime are not considered acceptable as the net effect is often to reduce code quality and medium term productivity On-site customer A representative of the end-user of the system (the customer) should be available full time for the use of the XP team. In an extreme programming process, the customer is a member of the development team and is responsible for bringing system requirements to the team for implementation.

Influential XP practices

• Extreme programming has a technical focus and is

not easy to integrate with management practice in

most organizations.

• Consequently, while agile development uses

practices from XP, the method as originally defined is

not widely used.

• Key practices

 User stories for specification

 Refactoring

 Test-first development

 Pair programming

User stories for requirements

• In XP, a customer or user is part of the XP team and

is responsible for making decisions on requirements.

• User requirements are expressed as user stories or

scenarios.

• These are written on cards and the development

team break them down into implementation tasks.

These tasks are the basis of schedule and cost

estimates.

• The customer chooses the stories for inclusion in the

next release based on their priorities and the

schedule estimates.

Refactoring (2)

• Programming team look for possible software improvements and make these improvements even where there is no immediate need for them.
• This improves the understandability of the software and so reduces the need for documentation.
• Changes are easier to make because the code is well-structured and clear.
• However, some changes requires architecture refactoring and this is much more expensive.

Test-first development

• 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.  Incremental test development from scenarios.  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.

Customer involvement

• The role of the customer in the testing process is to help develop acceptance tests for the stories that are to be implemented in the next release of the system.
• The customer who is part of the team writes tests as development proceeds. All new code is therefore validated to ensure that it is what the customer needs.
• However, people adopting the customer role have limited time available and so cannot work full-time with the development team. They may feel that providing the requirements was enough of a contribution and so may be reluctant to get involved in the testing process.

Test automation

• Test automation means that tests are written as executable components before the task is implemented

 These testing components should be stand-alone, should

simulate the submission of input to be tested and should check

that the result meets the output specification. An automated

test framework (e.g. Junit) is a system that makes it easy to

write executable tests and submit a set of tests for execution.

• As testing is automated, there is always a set of tests that can be quickly and easily executed

 Whenever any functionality is added to the system, the tests

can be run and problems that the new code has introduced can

be caught immediately.