Software Life Cycle Models

Software Life Cycle Models History The "waterfall model", documented in 1970 by Royce was the first publicly documented life cycle model. The model was developed to help cope with the increasing complexity of aerospace products. The waterfall model followed a documentation driven paradigm. The next revolutionary new look at the development lifecycle was the "spiral model", presented by Boehm in 1985. The spiral model is focused on risk management.

Methods Life cycle models describe the interrelationships between software development phases. The common life cycle models are: • • • • • • •

spiral model waterfall model throwaway prototyping model evolutionary prototyping model incremental/iterative development reusable software model automated software synthesis

Because the life cycle steps are described in very general terms, the models are adaptable and their implementation details will vary among different organizations. The spiral model is the most general. Most life cycle models can in fact be derived as special instances of the spiral model. Organizations may mix and match different life cycle models to develop a model more tailored to their products and capabilities.

Learn A software life cycle model depicts the significant phases or activities of a software project from conception until the product is retired. It specifies the relationships between project phases, including transition criteria, feedback mechanisms, milestones, baselines, reviews, and deliverables. Typically, a life cycle model addresses the following phases of a software project: requirements phase, design phase, implementation, integration, testing, operations and maintenance. Much of the motivation behind utilizing a life cycle model is to provide structure to avoid the problems of the "undisciplined hacker".

Evaluate Spiral Model

The spiral model is the most generic of the models. Most life cycle models can be derived as special cases of the spiral model. The spiral uses a risk management approach to software development. Some advantages of the spiral model are: • • • • • • • • •

defers elaboration of low risk software elements incorporates prototyping as a risk reduction strategy gives an early focus to reusable software accommodates life-cycle evolution, growth, and requirement changes incorporates software quality objectives into the product focus on early error detection and design flaws sets completion criteria for each project activity to answer the question: "How much is enough?" uses identical approaches for development and maintenance can be used for hardware-software system development

Waterfall Model The least flexible and most obsolete of the life cycle models. Well suited to projects that has low risk in the areas of user interface and performance requirements, but high risk in budget and schedule predictability and control. Throwaway Prototyping Model Useful in "proof of concept" or situations where requirements and user's needs are unclear or poorly specified. The approach is to construct a quick and dirty partial implementation of the system during or before the requirements phase. Evolutionary Prototyping Model Use in projects that have low risk in such areas as losing budget, schedule predictability and control, large-system integration problems, or coping with information sclerosis, but high risk in user interface design. Incremental/iterative Development The process for constructing several partial deliverables, each having incrementally more functionality. Automated Software Synthesis This process relies on tools to transform requirements into operational code. Formal requirements are created and maintained using specification tools. This is an active research area, and practical tools for this approach are yet to be developed.

Life Cycle of Testing This article explains about Differant steps in Life Cycle of Testing Process. in Each phase of the development process will have a specific input and a specific output. Once the project is confirmed to start, the phases of the development of project can be divided into the following phases:

• • • • •

Software requirements phase. Software Design Implementation Testing Maintenance

In the whole development process, testing consumes highest amount of time. But most of the developers oversee that and testing phase is generally neglected. As a consequence, erroneous software is released. The testing team should be involved right from the requirements stage itself. The various phases involved in testing, with regard to the software development life cycle are: 1. Requirements stage 2. Test Plan 3. Test Design. 4. Design Reviews 5. Code Reviews 6. Test Cases preparation. 7. Test Execution 8. Test Reports. 9. Bugs Reporting 10. Reworking on patches. 11. Release to production. Requirements Stage Normally in many companies, developers itself take part in the requirements stage. Especially for product-based companies, a tester should also be involved in this stage. Since a tester thinks from the user side whereas a developer can’t. A separate panel should be formed for each module comprising a developer, a tester and a user. Panel meetings should be scheduled in order to gather everyone’s view. All the requirements should be documented properly for further use and this document is called “Software Requirements Specifications”. Test Plan Without a good plan, no work is a success. A successful work always contains a good plan. The testing process of software should also require good plan. Test plan document is

the most important document that brings in a process – oriented approach. A test plan document should be prepared after the requirements of the project are confirmed. The test plan document must consist of the following information: • Total number of features to be tested. • Testing approaches to be followed. • The testing methodologies • Number of man-hours required. • Resources required for the whole testing process. • The testing tools that are to be used. • The test cases, etc Test Design Test Design is done based on the requirements of the project. Test has to be designed based on whether manual or automated testing is done. For automation testing, the different paths for testing are to be identified first. An end to end checklist has to be prepared covering all the features of the project. The test design is represented pictographically. The test design involves various stages. These stages can be summarized as follows: • The different modules of the software are identified first. • Next, the paths connecting all the modules are identified. Then the design is drawn. The test design is the most critical one, which decides the test case preparation. So the test design assesses the quality of testing process. Test Cases Preparation Test cases should be prepared based on the following scenarios: • Positive scenarios • Negative scenarios • Boundary conditions and • Real World scenarios This article talks about many interesting things like what's the Case for Automated Testing, Why Automate the Testing Process?, Using Testing Effectively, Reducing Testing Costs, Replicating testing across different platforms, Greater Application Coverage, Results Reporting, Understanding the Testing Process, Typical Testing Steps, Identifying Tests Requiring Automation, Task Automation and Test Set-Up and Who Should Be Testing?.

The Case for Automated Testing Today, rigorous application testing is a critical part of virtually all software development projects. As more organizations develop mission – critical systems to

support their business activities, the need is greatly increased for testing methods that support business objectives. It is necessary to ensure that these systems are reliable, built according to specification and have the ability to support business processes. Many internal and external factors are forcing organizations to ensure a high level of software quality and reliability. Why Automate the Testing Process? In the past, most software tests were performed using manual methods. This required a large staff of test personnel to perform expensive and time-consuming manual test procedures. Owing to the size and complexity of today’s advanced software applications, manual testing is no longer a viable option for most testing situations. Using Testing Effectively By definition, testing is a repetitive activity. The methods that are employed to carry out testing (manual or automated) remain repetitious throughout the development life cycle. Automation of testing processes allows machines to complete the tedious, repetitive work while human personnel perform other tasks. Automation eliminates the required “think time” or “read time” necessary for the manual interpretation of when or where to click the mouse. An automated test executes the next operation in the test hierarchy at machine speed, allowing test to be completed many times faster than the fastest individual. Automated test also perform load/stress testing very effectively. Reducing Testing Costs The cost of performing manual testing is prohibitive when compared to automated methods. The reason is that computers can execute instructions many times faster and with fewer errors than individuals. Many automated testing tools can replicate the activity of a large number of users (and their associated transactions) using a single computer. Therefore, load/stress testing using automated methods requires only a fraction of the computer hardware that would be necessary to complete a manual test. Replicating testing across different platforms Automation allows the testing organization to perform consistent and repeatable test. When applications need to be deployed across different hardware or software platforms, standard or benchmark tests can be created and repeated on target platforms to ensure that new platforms operate consistently. Greater Application Coverage The productivity gains delivered by automated testing allow and encourage organization to test more often and more completely. Greater application test coverage also reduces the risk if exposing users to malfunctioning or non-compliant software.

Results Reporting Full-featured automated testing systems also produce convenient test reporting and analysis. These reports provide a standardized measure of test status and results, thus allowing more accurate interpretation of testing outcomes. Manual methods require the user to self-document test procedures and test results. Usability Engineering, an empirical science has quite a simple definition. It studies the human interaction and cognitive behavior of an individual with respect to performing as task. It could be as simple as a driving a vehicle or using a product. Users interaction in performing a task should be in sync with the workflow of the product. Usability Engineering as a science helps in achieving this goal.

Usability for a Product A Product should be usable. It means that people can use a product easily and efficiently to accomplish their own tasks. A product, which is usable, enables workers to concentrate on their tasks and to do real work, rather than on the tools they use to perform their tasks. A usable product has the following characteristics: • It’s easy to learn • Efficient to use • Provides quick recovery from errors • Easy to remember • Enjoyable to use • Visually pleasing Usability applies to every aspect of a product with which a person interacts (hardware, software, menus, icons, messages, documentation, training, and on-line help). Every design and development decision made throughout the product cycle has an impact on that product’s usability. As customers depend more and more on software to get their jobs done and become more critical consumers, usability can be the critical factor that ensures that products will be used. Usability Engineering Techniques Usability engineering involves a variety of techniques that can provide important information about how customers work with your product. Different techniques are used at different stages of a product’s development. For example, as processes are being engineered and requirements are being developed, observations and interviews may be the techniques of choice. Later in the development cycle, as the “look and feel” of a product is being designed, benchmarking, prototyping and participatory design may be useful techniques. Once a design has been determined,

usability testing may be used more appropriately. Usability is an iterative process, just like software development. The usability process works best if it is done in partnership with product development. Some usability techniques include 1. User and task observations – observing users at their jobs, identifying their typical work tasks and procedures, analyzing their work processes, and understanding people in the context of their work. 2. Interviews, focus groups and questionnaires – meeting with users, finding out about their preferences, experiences and needs. 3. Benchmarking and competitive analysis – evaluating the usability of similar products in the marketplace. 4. Participatory design - participating in design and bringing the user’s perspective to the early stages of development. 5. Paper prototyping – including users early in the development process through prototypes prepared on paper before coding begins. 6. Creation of guidelines - helping to assure consistency in design through development of standards and guidelines. 7. Heuristic evaluations - evaluating software against accepted usability principles and making recommendations to enhance usability. 8. Usability testing - observing users performing real tasks with the application, recording what they do, analyzing the results and recommending appropriate changes. Metrics • Overall feedback rating given by customer on execution of project / product service • Effort Variance • Schedule Variance • Cost of Quality • Test Design Productivity • Testing Productivity • Testing efficiency • Customer Issues • Utilization of allocated effort • Test design coverage • Test execution coverage