Lecture 3 - Agile Software Development (CSE241/CMM341) PDF

CPT 441 CSE241/CMM341 Software Quality Assurance & Testing Foundations of Software Engineering Photo credit: Dreamstime.com Topic 3: Agile Software Development CCBY AMK & LCY, USM 2023...

CPT 441 CSE241/CMM341 Software Quality Assurance & Testing Foundations of Software Engineering Photo credit: Dreamstime.com Topic 3: Agile Software Development CCBY AMK & LCY, USM 2023 1  CSE241 Course Content We l e a d Foundations 1. Introduction to Software Engineering of Software 2. Software Processes 3. Agile Software Development Engineering 4. Requirements Engineering 5. System Modeling 6. Software Design Strategies and Methods 7. Architectural Design & Implementation 8. Software Testing 9. Software Evolution 10. Project Management 11. Project planning 12. Quality Management 13. Configuration Management 2  Topic 3: Agile Software Development Contents AGILE METHODS AGILE DEVELOPMENT AGILE PROJECT SCALING AGILE TECHNIQUES MANAGEMENT METHODS 3  Learning Outcomes Understand the rationale for agile Know about important agile software development methods, the development practices such as user agile manifesto, and the differences stories, refactoring, pair between agile and plan-driven programming and test-first development development Understand the issues of scaling agile development methods and Understand the Scrum approach to combining agile approaches with agile project management plan-driven approaches in the development of large software systems. 4 Recall Topic 2…… Categorization of Software Processes Plan-driven processes all of the process activities are planned in advance progress is measured against the plan Agile processes planning is incremental easier to change the process to reflect changing customer requirements RAPID SOFTWARE DEVELOPMENT 5 Rapid Software Development https://www.youtube.com/watch?v=Z9QbYZh1YXY 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. Plan-driven development is essential for some types of system but does not meet these business needs. This Photo by Unknown author is licensed under CC BY-SA. Agile development methods aim was to radically reduce the delivery time for working software systems 6  The processes of specification, design and implementation are interleaved. Agile Methods no detailed system specification Characteristics design documentation is minimized or generated automatically by the programming environment. user requirements document : an outline definition of the most important characteristics of the system. 7  The system is developed in a series of increments. Agile Methods End-users and other system stakeholders are Characteristics involved in specifying and evaluating each increment Proposed changes to the software and new requirements should be implemented in a later version of the system. 8  Extensive tool support is used to support the development process. Agile Methods Characteristics automated testing tools tools to support configuration management and system integration tools to automate user interface production 9  Plan-driven and agile development  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 Agile Are based on an iterative approach to software development methods 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. 11 This Photo by Unknown author is licensed under CC BY-SA-NC.  Principle Description Customer Customers should be closely involved The Principles of involvement throughout the development process. Agile Methods Their role is to provide and prioritize new system requirements and to evaluate the iterations of the system. Incremental The software is developed in increments delivery with the customer specifying the requirements to be included in each increment. People not The skills of the development team process should be recognized and exploited. Team members should be left to develop their own ways of working without prescriptive processes.  The Principles of Agile Methods Principle Description Embrace change Expect the system requirements to change and so design the system to accommodate these changes. The principles of agile methods 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.  Agile method applicability Product development where a software Virtually all software products company is developing a small or and apps are now developed medium-sized product for sale. 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. 15  Topic 3: Agile Software Development Contents AGILE METHODS AGILE AGILE PROJECT SCALING AGILE DEVELOPMENT MANAGEMENT METHODS TECHNIQUES 16  Extreme Programming A very influential agile method, developed in the late 1990s, that introduced a range of agile development techniques. 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. 17 17 The extreme programming release cycle 18 Extreme Principle or Description programming practice practices Incremental Requirements are recorded on story cards and planning 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’. 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. 19 Extreme Principle or practice Description programming Test-first An automated unit test framework is used to write practices development 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. Pair programming Developers work in pairs, checking each other’s work and providing the support to always do a good job. Collective The pairs of developers work on all areas of the ownership system, so that no islands of expertise develop and all the developers take responsibility for all of the code. Anyone can change anything. 20  Principle or Description Extreme practice programming Continuous As soon as the work on a task is complete, it is practices integration integrated into the whole system. After any such integration, all the unit tests in the system must pas 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. 21  Incremental development Customer involvement is supported through means continuous small, frequent system customer engagement with releases. the team. XP and People, not process, are Change supported through supported through pair agile programming, collective regular system releases to customers, test-first ownership and a process principles that avoids long working development, refactoring to avoid code degeneration, and hours. (recap) continuous integration Maintaining simplicity of new functionality. through constant refactoring of code to improves code quality and by using simple designs 22 Key XP practices User stories for specification Refactoring Test-first development (TDD) Pair programming 23 User stories for specification Refactoring Test-first development A customer or user Pair programming part of the XP team responsible for making decisions on requirements. User requirements User stories expressed as user stories or scenarios. for requirements written on cards and the development team break them down into implementation tasks. https://youtu.be/LGeDZmrWwsw 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. 24  User stories for specification Refactoring Refactoring Test-first development Pair programming https://youtu.be/LsLniadcRTw Conventional wisdom in software engineering is to design for change. It is worth spending time and effort anticipating changes as this reduces costs later in the life cycle. XP, however, maintains that this is not worthwhile as changes cannot be reliably anticipated. Rather, it proposes constant code improvement (refactoring) to make changes easier when they have to be implemented. 25  User stories for specification Refactoring Refactoring Test-first development Pair programming 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. 26  User stories for specification Refactoring Test-first development Pair programming Examples of Refactoring The replacement of Tidying up and Re-organization of a inline code with renaming attributes class hierarchy to calls to methods and methods to remove duplicate that have been make them easier code. included in a to understand. program library. 27 User stories for specification Refactoring Test-first development Pair programming An approach where the program is tested after every change has been made. Test-first XP testing features: development Test-first development. https://youtu.be/uGaNkTahrIw 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. 28 User stories for specification Refactoring Test-first development Writing tests before code clarifies the requirements Pair programming to be implemented. Test-driven development Tests are written as programs rather than data so that they can be executed automatically. The test includes (TDD) 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. 29  User stories for specification Customer involvement in TDD Refactoring Test-first development Pair programming To help develop acceptance tests for the stories that are to be implemented in the next release of the system. Writes tests together with team as development proceeds. All new code is validated to ensure that it is what the customer needs. https://blog.hubspot.com/service/customer-orientation However, in real life customer have limited time available and so cannot work full-time with the development team. Only provides the requirements and not involved in the testing process. 30  User stories for specification Test Automation Refactoring Test-first development Pair programming Essential for test-first development Tests are written as executable components before the task is implemented Testing components should : stand-alone simulate the submission of input to be tested check that the result meets the output specification An automated test framework is a system that makes it easy to write executable tests and submit a set of tests for execution. (e.g. Junit) 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. 31  User stories for specification Problems with test-first development Refactoring Test-first development Pair programming Programmers prefer programming to testing and sometimes they take short cuts when writing tests. For example, they may write incomplete tests that do not check for all possible exceptions that may occur. Some tests can be very difficult to write incrementally. For example, in a complex user interface, it is often difficult to write unit tests for the code that implements the ‘display logic’ and workflow between screens. It difficult to judge the completeness of a set of tests. Although you may have a lot of system tests, your test set may not provide complete coverage. This Photo by Unknown author is licensed under CC BY-SA. 32  User stories for specification Refactoring Test-first development programmers working in pairs, developing Pair programming code together. develop common ownership of code and spreads knowledge across the team. Pair Programming serves as an informal review process as each line of code is looked at by more https://youtu.be/ET3Q6zNK3Io than 1 person. encourages refactoring as the whole team can benefit from improving the system code. 33 Pair programming Programmers sit together at the same computer 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. 34  Topic 3: Agile Software Development Contents AGILE METHODS AGILE DEVELOPMENT AGILE PROJECT SCALING AGILE TECHNIQUES MANAGEMENT METHODS 35 Agile project management The principal responsibility of software project managers is to manage the project so that the software is delivered on time and within the planned budget for the project. Agile project management requires a different approach, which is adapted to incremental development and the practices used in agile methods. 36  Scrum https://youtu.be/9TycLR0TqFA An agile method that focuses on managing iterative development rather than specific agile practices. There are three phases in Scrum. An outline planning phase where you establish the general objectives for the project and design the software architecture. A series of sprint cycles, where each cycle develops an increment of the system. Project closure phase wraps up the project, completes required documentation such as system help frames and user manuals and assesses the lessons learned from the project. 37  Scrum Terminology Scrum term Definition Development A self-organizing group of software developers, which team should be no more than 7 people. They are responsible for developing the software and other essential project documents. Potentially The software increment that is delivered from a sprint. shippable product The idea is that this should be ‘potentially shippable’ increment which means that it is in a finished state and no further work, such as testing, is needed to incorporate it into the final product. In practice, this is not always achievable. 38  Scrum Terminology Scrum term Definition Product backlog This is a list of ‘to do’ items which the Scrum team must tackle. They may be feature definitions for the software, software requirements, user stories or descriptions of supplementary tasks that are needed, such as architecture definition or user documentation. Product owner An individual (or possibly a small group) whose job is to identify product features or requirements, prioritize these for development and continuously review the product backlog to ensure that the project continues to meet critical business needs. The Product Owner can be a customer but might also be a product manager in a software company or other stakeholder representative. 39  Scrum terminology Scrum term Definition Scrum A daily meeting of the Scrum team that reviews progress and prioritizes work to be done that day. Ideally, this should be a short face-to-face meeting that includes the whole team. Scrum The ScrumMaster is responsible for ensuring that the Scrum Master process is followed and guides the team in the effective use of Scrum. He or she is responsible for interfacing with the rest of the company and for ensuring that the Scrum team is not diverted by outside interference. The Scrum developers are adamant that the ScrumMaster should not be thought of as a project manager. Others, however, may not always find it easy to see the difference. 40  Scrum terminology Scrum term Definition Sprint A development iteration. Sprints are usually 2-4 weeks long. Velocity An estimate of how much product backlog effort that a team can cover in a single sprint. Understanding a team’s velocity helps them estimate what can be covered in a sprint and provides a basis for measuring improving performance. 41 Scrum sprint cycle 42 The Scrum sprint cycle Sprints are fixed length, normally 2–4 weeks. The starting point for planning is the product backlog, which is the list of work to be done on the project. The selection phase involves all of the project team who work with the customer to select the features and functionality from the product backlog to be developed during the sprint. 43 The Sprint cycle During this stage the team is isolated from the customer Once these are agreed, the and the organization, with all team organize themselves to communications channelled develop the software. through the so-called ‘Scrum master’. The role of the Scrum master At the end of the sprint, the is to protect the development work done is reviewed and team from external presented to stakeholders. The distractions. next sprint cycle then begins. 44 Teamwork in Scrum The ‘Scrum master’ is a The whole team attends facilitator who arranges short daily meetings daily meetings, tracks the (Scrums) where all team backlog of work to be members share done, records decisions, information, describe measures progress their progress since the against the backlog and last meeting, problems communicates with that have arisen and what customers and is planned for the management outside of following day. the team. 45 Scrum benefits The product is broken down into a set of manageable and understandable chunks. Unstable requirements do not hold up progress. The whole team have visibility of everything and consequently team communication is improved. Customers see on-time delivery of increments and gain feedback on how the product works. Trust between customers and developers is established and a positive culture is created in which everyone expects the project to succeed. 46 Distributed Scrum 47  Summary : Scrum An agile method that focuses on managing iterative development rather than specific agile practices. There are three phases in Scrum. Scrum sprint cycle An outline planning phase. A series of sprint cycles Project closure phase wraps up the project 48  XP and Scrum discussions XP- incorporated in their own development processes but commonly, used in conjunction wih management-focused agile method i.e Scrum Scrum→ framework to organize agile projects difference between Scrum and XP is subtle Scrum is just a framework for product development, Scrum is a container where you can add other practices. XP is one of those practices that you can do within Scrum framework. XP is one of the missing piece Scrum team need to deliver great quality products. Ref: https://qr.page/g/UGeFko1hq8 49 Ref: https://qr.page/g/UGeFko1hq8 XP and Scrum discussions XP- incorporated in their own development processes but commonly, used in conjunction wih management-focused agile method i.e Scrum Scrum→ framework to organize agile projects difference between Scrum and XP is subtle Scrum is just a framework for product development, Scrum is a container where you can add other practices. XP is one of those practices that you can do within Scrum framework. XP is one of the missing piece Scrum team need to deliver great quality products. Ref: https://qr.page/g/UGeFko1hq8 50  Topic 3: Agile Software Development Contents AGILE METHODS AGILE DEVELOPMENT AGILE PROJECT SCALING AGILE TECHNIQUES MANAGEMENT METHODS 51  Agile methods have proved to be successful for small and medium sized projects that can be developed by a small co-located team. Scaling agile methods It is sometimes argued that the success of these methods comes because of improved communications which is possible when everyone is working together. 52  Scaling out and scaling up ‘Scaling up’ : ‘Scaling out’ using agile methods for how agile methods can be developing large software introduced across a large systems that cannot be organization with many years developed by a small team. of software development experience. 53 Practical problems with agile methods The informality of agile development is incompatible with the legal approach to contract definition that is commonly used in large companies. Agile methods are most appropriate for new software development rather than software maintenance. Yet the majority of software costs in large companies come from maintaining their existing software systems. Agile methods are designed for small co-located teams yet much software development now involves worldwide distributed teams. 54 Contractual issues Most software contracts for custom systems are based around a specification, which sets out what has to be implemented by the system developer for the system customer. However, this precludes interleaving specification and development as is the norm in agile development. A contract that pays for developer time rather than functionality is required. However, this is seen as a high risk on many legal departments because what has to be delivered cannot be guaranteed. 55 Agile methods and software maintenance Most organizations spend more on maintaining existing software than they do on new software development. So, if agile methods are to be successful, they have to support maintenance as well as original development. Two key issues: Are systems that are developed using an Can agile methods be used effectively agile approach maintainable, given the for evolving a system in response to emphasis in the development process of customer change requests? minimizing formal documentation? Problems may arise if original development team cannot be maintained. 56 Agile maintenance Key problems are: Keeping customers Lack of product Maintaining the continuity involved in the documentation of the development team development process Agile development relies on the development team knowing and understanding what has to be done. For long-lifetime systems, this is a real problem as the original developers will not always work on the system. 57  Is it important to have a very detailed specification and design before moving to implementation? Agile vs If so, you probably need to use a plan-driven approach. plan- Is an incremental delivery strategy, where you deliver the software to customers and get rapid feedback from them, realistic? driven If so, consider using agile methods. methods How large is the system that is being developed? Agile methods are most effective when the system can be developed with a small co-located team who can communicate informally. This may not be possible for large systems that require larger development teams so a plan-driven approach may have to be used. 58 Agile principles and organizational practice 59 System issues How large is the system being developed? Agile methods are most effective a relatively small co- located team who can communicate informally. What type of system is being developed? Systems that require a lot of analysis before implementation need a fairly detailed design to carry out this analysis. What is the expected system lifetime? Long-lifetime systems require documentation to communicate the intentions of the system developers to the support team. Is the system subject to external regulation? If a system is regulated you will probably be required to produce detailed documentation as part of the system safety case. 60  It is sometimes argued that agile How good are the methods require higher skill levels designers and than plan-based approaches in which programmers in the programmers simply translate a People development team? detailed design into code. and teams How is the development team Design documents may be required if the team is dsitributed. organized? What support IDE support for visualisation and technologies are program analysis is essential if design available? documentation is not available. 61  Organizational issues Traditional engineering Is it standard organizations have a organizational practice to culture of plan-based develop a detailed development, as this is system specification? the norm in engineering. Will customer Can informal agile representatives be available development fit into the to provide feedback of organizational culture of system increments? detailed documentation? 62  6 Factors in large systems Agile methods for large systems 63 Agile methods for large systems Large systems are usually collections of separate, communicating systems, where separate teams develop each system. Frequently, these teams are working in different places, sometimes in different time zones. Large systems are ‘brownfield systems’, that is they include and interact with a number of existing systems. Many of the system requirements are concerned with this interaction and so don’t really lend themselves to flexibility and incremental development. Where several systems are integrated to create a system, a significant fraction of the development is concerned with system configuration rather than original code development. 64 Agile methods for large systems Large systems and their development processes are often constrained by external rules and regulations limiting the way that they can be developed. Large systems have a long procurement and development time. It is difficult to maintain coherent teams who know about the system over that period as, inevitably, people move on to other jobs and projects. Large systems usually have a diverse set of stakeholders. It is practically impossible to involve all of these different stakeholders in the development process. 65 IBM’s agility at scale model 66  A completely incremental approach to requirements engineering is impossible. There cannot be a single product owner or customer representative. Scaling up For large systems development, it is not possible to to large focus only on the code of the system. systems Cross-team communication mechanisms have to be designed and used. Continuous integration is practically impossible. However, it is essential to maintain frequent system builds and regular releases of the system. 67  Multi-team Scrum Role replication Product architects Release alignment Scrum of Scrums Each team has a Each team The dates of There is a daily Product Owner chooses a product releases Scrum of Scrums for their work product from each team where component and architect and are aligned so representatives ScrumMaster. these architects that a from each team collaborate to demonstrable meet to discuss design and and complete progress and evolve the system is plan work to be overall system produced. done. architecture. 68  Project managers who do not have experience of agile methods may be reluctant to accept the risk of a new approach. Large organizations often have quality procedures and standards Agile that all projects are expected to follow and, because of their bureaucratic nature, these are likely to be incompatible with agile methods methods. across Agile methods seem to work best when team members have a relatively high skill level. However, within large organizations, organizations there are likely to be a wide range of skills and abilities. There may be cultural resistance to agile methods, especially in those organizations that have a long history of using conventional systems engineering processes. 69 Key points (1/2) Agile methods are incremental development methods that focus on rapid software development, frequent releases of the software, reducing process overheads by minimizing documentation and producing high-quality code. Agile development practices include User stories for system specification Frequent releases of the software, Continuous software improvement Test-first development Customer participation in the development team. 70 Key points (2/2) Scrum is an agile method that provides a project management framework. It is centred round a set of sprints, which are fixed time periods when a system increment is developed. Many practical development methods are a mixture of plan-based and agile development. Scaling agile methods for large systems is difficult. Large systems need up-front design and some documentation and organizational practice may conflict with the informality of agile approaches. 71