Agile SDLC model is a combination of iterative and incremental process models with focus on process adaptability and customer satisfaction by rapid delivery of working software product.
Agile Methods break the product into small incremental builds. These builds are provided in iterations. Each iteration typically lasts from about one to three weeks. Every iteration involves cross functional teams working simultaneously on various areas like planning, requirements analysis, design, coding, unit testing, and acceptance testing.
At the end of the iteration a working product is displayed to the customer and important stakeholders.
What is Agile?
Agile model believes that every project needs to be handled differently and the existing methods need to be tailored to best suit the project requirements. In agile the tasks are divided to time boxes (small time frames) to deliver specific features for a release.
Iterative approach is taken and working software build is delivered after each iteration. Each build is incremental in terms of features; the final build holds all the features required by the customer.
Here is a graphical illustration of the Agile Model:
Agile thought process had started early in the software development and started becoming popular with time due to its flexibility and adaptability.
The most popular agile methods include Rational Unified Process (1994), Scrum (1995), Crystal Clear, Extreme Programming (1996), Adaptive Software Development, Feature Driven Development, and Dynamic Systems Development Method (DSDM) (1995). These are now collectively referred to as agile methodologies, after the Agile Manifesto was published in 2001.
Following are the Agile Manifesto principles
- Individuals and interactions - in agile development, self-organization and motivation are important, as are interactions like co-location and pair programming.
- Working software - Demo working software is considered the best means of communication with the customer to understand their requirement, instead of just depending on documentation.
- Customer collaboration - As the requirements cannot be gathered completely in the beginning of the project due to various factors, continuous customer interaction is very important to get proper product requirements.
- Responding to change - agile development is focused on quick responses to change and continuous development.
Agile Vs Traditional SDLC Models
Agile is based on the adaptive software development methods where as the traditional SDLC models like waterfall model is based on predictive approach.
Predictive teams in the traditional SDLC models usually work with detailed planning and have a complete forecast of the exact tasks and features to be delivered in the next few months or during the product life cycle. Predictive methods entirely depend on the requirement analysis and planning done in the beginning of cycle. Any changes to be incorporated go through a strict change control management and prioritization.
Agile uses adaptive approach where there is no detailed planning and there is clarity on future tasks only in respect of what features need to be developed. There is feature driven development and the team adapts to the changing product requirements dynamically. The product is tested very frequently, through the release iterations, minimizing the risk of any major failures in future.
Customer interaction is the backbone of Agile methodology, and open communication with minimum documentation are the typical features of Agile development environment. The agile teams work in close collaboration with each other and are most often located in the same geographical location.
Why Agile?
Agile development methodology provides opportunities to assess the direction of a project throughout the development lifecycle. This is achieved through regular cadences of work, known as sprints or iterations, at the end of which teams must present a potentially shippable product increment. By focusing on the repetition of abbreviated work cycles as well as the functional product they yield, agile methodology is described as “iterative” and “incremental.” In waterfall, development teams only have one chance to get each aspect of a project right. In an agile paradigm, every aspect of development — requirements, design, etc. — is continually revisited throughout the lifecycle. When a team stops and re-evaluates the direction of a project every two weeks, there’s always time to steer it in another direction.
The results of this “inspect-and-adapt” approach to development greatly reduce both development costs and time to market. Because teams can develop software at the same time they’re gathering requirements, the phenomenon known as “analysis paralysis” is less likely to impede a team from making progress. And because a team’s work cycle is limited to two weeks, it gives stakeholders recurring opportunities to calibrate releases for success in the real world. Agile development methodology helps companies build the right product. Instead of committing to market a piece of software that hasn’t even been written yet, agile empowers teams to continuously replan their release to optimize its value throughout development, allowing them to be as competitive as possible in the marketplace. Development using an agile methodology preserves a product’s critical market relevance and ensures a team’s work doesn’t wind up on a shelf, never released.
- The agile software development emphasizes on four core values.
- Individual and team interactions over processes and tools
- Working software over comprehensive documentation
- Customer collaboration over contract negotiation
- Responding to change over following a plan
Agile versus Waterfall Method
Agile and Waterfall model are two different methods for software development process. Though they are different in their approach, both methods are useful at times, depending on the requirement and the type of the project.
Agile Model
Waterfall Model
- Agile method proposes incremental and iterative approach to software design
- Development of the software flows sequentially from start point to end point.
- The agile process is broken into individual models that designers work on
- The design process is not broken into an individual models
- The customer has early and frequent opportunities to look at the product and make decision and changes to the project
- The customer can only see the product at the end of the project
- Agile model is considered unstructured compared to the waterfall model
- Waterfall model are more secure because they are so plan oriented
- Small projects can be implemented very quickly. For large projects, it is difficult to estimate the development time.
- All sorts of project can be estimated and completed.
- Error can be fixed in the middle of the project.
- Only at the end, the whole product is tested. If the requirement error is found or any changes have to be made, the project has to start from the beginning
- Development process is iterative, and the project is executed in short (2-4) weeks iterations. Planning is very less.
- The development process is phased, and the phase is much bigger than iteration. Every phase ends with the detailed description of the next phase.
- Documentation attends less priority than software development
- Documentation is a top priority and can even use for training staff and upgrade the software with another team
- Every iteration has its own testing phase. It allows implementing regression testing every time new functions or logic are released.
- Only after the development phase, the testing phase is executed because separate parts are not fully functional.
- In agile testing when an iteration end, shippable features of the product is delivered to the customer. New features are usable right after shipment. It is useful when you have good contact with customers.
- All features developed are delivered at once after the long implementation phase.
- Testers and developers work together
- Testers work separately from developers
- At the end of every sprint, user acceptance is performed
- User acceptance is performed at the end of the project.
- It requires close communication with developers and together analyse requirements and planning
- Developer does not involve in requirement and planning process. Usually, time delays between tests and coding
Agile Model
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Waterfall Model
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Methodologies of Agile Testing
There are various methods present in agile testing, and those are listed below:
Scrum
SCRUM is an agile development method which concentrates specifically on how to manage tasks within a team based development environment. Basically, Scrum is derived from activity that occurs during a rugby match. Scrum believes in empowering the development team and advocates working in small teams (say- 7 to 9 members). It consists of three roles, and their responsibilities are explained as follows:
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Scrum Master
- Master is responsible for setting up the team, sprint meeting and removes obstacles to progress
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Product owner
- The Product Owner creates product backlog, prioritizes the backlog and is responsible for the delivery of the functionality at each iteration
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Scrum Team
- Team manages its own work and organizes the work to complete the sprint or cycle
Scrum Master
- Master is responsible for setting up the team, sprint meeting and removes obstacles to progress
Product owner
- The Product Owner creates product backlog, prioritizes the backlog and is responsible for the delivery of the functionality at each iteration
Scrum Team
- Team manages its own work and organizes the work to complete the sprint or cycle
Product Backlog
This is a repository where requirements are tracked with details on the no of requirements to be completed for each release. It should be maintained and prioritized by product owner, and it should be distributed to the scrum team. Team can also request for a new requirement addition or modification or deletion
Scrum Practices
Practices are described in detailed:
Process flow of Scrum:
Process flow of scrum testing is as follows:
- Each iteration of a scrum is known as Sprint
- Product backlog is a list where all details are entered to get end product
- During each Sprint, top items of Product backlog are selected and turned into Sprint backlog
- Team works on the defined sprint backlog
- Team checks for the daily work
- At the end of the sprint, team delivers product functionality
eXtreme Programming (XP)
Extreme Programming technique is very helpful when there is constantly changing demands or requirements from the customers or when they are not sure about the functionality of the system. It advocates frequent "releases" of the product in short development cycles, which inherently improves the productivity of the system and also introduces a checkpoint where any customer requirements can be easily implemented. The XP develops software keeping customer in the target.
Business requirements are gathered in terms of stories. All those stories are stored in a place called the parking lot.
In this type of methodology, releases are based on the shorter cycles called Iterations with span of 14 days time period. Each iteration includes phases like coding, unit testing and system testing where at each phase some minor or major functionality will be built in the application.
Phases of eXtreme programming:
There are 6 phases available in Agile XP method, and those are explained as follows:
Planning
- Identification of stakeholders and sponsors
- Infrastructure Requirements
- Security related information and gathering
- Service Level Agreements and its conditions
Analysis
- Capturing of Stories in Parking lot
- Prioritize stories in Parking lot
- Scrubbing of stories for estimation
- Define Iteration SPAN(Time)
- Resource planning for both Development and QA teams
Design
- Break down of tasks
- Test Scenario preparation for each task
- Regression Automation Framework
Execution
- Coding
- Unit Testing
- Execution of Manual test scenarios
- Defect Report generation
- Conversion of Manual to Automation regression test cases
- Mid Iteration review
- End of Iteration review
Wrapping
- Small Releases
- Regression Testing
- Demos and reviews
- Develop new stories based on the need
- Process Improvements based on end of iteration review comments
Closure
- Pilot Launch
- Training
- Production Launch
- SLA Guarantee assurance
- Review SOA strategy
- Production Support
There are two storyboards available to track the work on a daily basis, and those are listed below for reference.
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Story Cardboard
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This is a traditional way of collecting all the stories in a board in the form of stick notes to track daily XP activities. As this manual activity involves more effort and time, it is better to switch to an online form.
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Online Storyboard
- Online tool Storyboard can be used to store the stories. Several teams can use it for different purposes.
Story Cardboard
- This is a traditional way of collecting all the stories in a board in the form of stick notes to track daily XP activities. As this manual activity involves more effort and time, it is better to switch to an online form.
Online Storyboard
- Online tool Storyboard can be used to store the stories. Several teams can use it for different purposes.
Crystal Methodologies
Crystal Methodology is based on three concepts
- Chartering: Various activities involved in this phase are creating a development team, performing a preliminary feasibility analysis, developing an initial plan and fine-tuning the development methodology
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Cyclic delivery: The main development phase consists of two or more delivery cycles, during which the
- Team updates and refines the release plan
- Implements a subset of the requirements through one or more program test integrate iterations
- Integrated product is delivered to real users
- Review of the project plan and adopted development methodology
- Wrap Up: The activities performed in this phase are deployment into the user environment, post- deployment reviews and reflections are performed.
Cyclic delivery: The main development phase consists of two or more delivery cycles, during which the
- Team updates and refines the release plan
- Implements a subset of the requirements through one or more program test integrate iterations
- Integrated product is delivered to real users
- Review of the project plan and adopted development methodology
Dynamic Software Development Method (DSDM)
DSDM is a Rapid Application Development (RAD) approach to software development and provides an agile project delivery framework. The important aspect of DSDM is that the users are required to be involved actively, and the teams are given the power to make decisions. Frequent delivery of product becomes the active focus with DSDM. The techniques used in DSDM are
- Time Boxing
- MoSCoW Rules
- Prototyping
The DSDM project consists of 7 phases
- Pre-project
- Feasibility Study
- Business Study
- Functional Model Iteration
- Design and build Iteration
- Implementation
- Post-project
Feature Driven Development (FDD)
This method is focused around "designing & building" features. Unlike other agile methods, FDD describes very specific and short phases of work that has to be accomplished separately per feature. It includes domain walkthrough, design inspection, promote to build, code inspection and design. FDD develops product keeping following things in the target
- Domain object Modeling
- Development by feature
- Component/ Class Ownership
- Feature Teams
- Inspections
- Configuration Management
- Regular Builds
- Visibility of progress and results
Lean Software Development
Lean software development method is based on the principle "Just in time production". It aims at increasing speed of software development and decreasing cost. Lean development can be summarized in seven steps.
- Eliminating Waste
- Amplifying learning
- Defer commitment (deciding as late as possible)
- Early delivery
- Empowering the team
- Building Integrity
- Optimize the whole
Kanban
Kanban originally emerged from Japanese word that means, a card containing all the information needed> to be done on the product at each stage along its path to completion. This framework or method is quite adopted in software testing method especially in agile testing.
Difference between Scrum and Kanban
Scrum
Kanban
- In scrum technique, test must be broken down so that they can be completed within one sprint
- No particular item size is prescribed
- Prescribes a prioritized product backlog
- Prioritization is optional
- Scrum team commits to a particular amount of work for the iteration
- Commitment is optional
- Burndown chart is prescribed
- No particular item size is prescribed
- Between each sprint, a scrum board is reset
- A Kanban board is persistent. It limits the number of items in workflow state
- It cannot add items to ongoing iteration
- It can add items whenever capacity is available
- WIP limited indirectly
- WIP limited directly
- Timeboxed iterations prescribed
- Timeboxed iterations optional
Scrum
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Kanban
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Agile metrics:
Metrics that can be collected for effective usage of Agile is:
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Drag Factor
- Effort in hours which do not contribute to sprint goal
- Drag factor can be improved by reducing number of shared resources, reducing the amount of non-contributing work
- New estimates can be increased by percentage of drag factor -New estimate = (Old estimate+drag factor)
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Velocity
- Amount of backlog converted to shippable functionality of sprint
- No of Unit Tests added
- Time taken to complete daily build
- Bugs detected in an iteration or in previous iterations
- Production defect leakage
Drag Factor
- Effort in hours which do not contribute to sprint goal
- Drag factor can be improved by reducing number of shared resources, reducing the amount of non-contributing work
- New estimates can be increased by percentage of drag factor -New estimate = (Old estimate+drag factor)
Velocity
- Amount of backlog converted to shippable functionality of sprint
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