ISTQB - Software development life cycle
- 1. Testing throughout software development lifecycle HOÀNG HIỀN
- 3. Contents 1. Software development lifecycle 2. Software development Model
- 4. Software Development and Software Testing Characteristics of good testing in software development lifecycle model • For every development activity, there is a corresponding test activity • Each test level has test objectives specific to that level • Test analysis and design for a given test level begin during the corresponding development activity • Testers participate in discussions to define and refine requirements and design, and are involved in reviewing work products (e.g., requirements, design, user stories, etc.) as soon as drafts are available
- 5. 1 Software development life cycle - phases 1. Requirement gathering and analysis 2. Design 3. Implementation or coding 4. Testing 5. Deployment 6. Maintenance
- 6. 2 Software development Model • Waterfall model • V model • Incremental model • RAD model • Agile model • Iterative model • Spiral model • Prototype model
- 8. Waterfall model Advantages •simple and easy to understand and use •easy to manage due to the rigidity of the model •phases are processed and completed one at a time. Phases do not overlap. •works well for smaller projects where requirements are very well understood. Disadvantages •When in the testing stage, it is very difficult to go back and change •No working software is produced until late during the life cycle. •High amounts of risk and uncertainty. •Not a good model for complex and object-oriented projects. • Poor model for long and ongoing projects. • Not suitable for the projects where requirements are at a moderate to high
- 9. Waterfall model When to Use • This model is used only when the requirements are very well known, clear and fixed. • Product definition is stable. • Technology is understood. • There are no ambiguous requirements • Ample resources with required expertise are available freely • The project is short.
- 10. V model
- 11. V model Advantages •Simple and easy to use. •Testing activities like planning, test designing happens well before coding. This saves a lot of time. Proactive defect tracking – that is defects are found at early stage. •Avoids the downward flow of the defects. •Works well for small projects where requirements are easily understood. •. Disadvantages •Very rigid and least flexible. •Software is developed during the implementation phase, so no early prototypes of the software are produced. •If any changes happen in midwayes happen in midway, then the test documents along with requirement documents has to be updated.
- 12. V model When to Use • The V-shaped model should be used for small to medium sized projects where requirements are clearly defined and fixed. • The V-Shaped model should be chosen when ample technical resources are available with needed technical expertise.
- 14. Incremental model Advantages •Generates working software quickly and early during the software life cycle. •Testing activities like planning, test designing happens well before coding. This saves a lot of time. Proactive defect tracking – that is defects are found at early stage. •Avoids the downward flow of the defects. Disadvantages •Needs good planning and design. •Needs a clear and complete definition of the whole system before it can be broken down and built incrementally. •Total cost is higher than waterfall.
- 15. Incremental model When to Use • This model can be used when the requirements of the complete system are clearly defined and understood. • Major requirements must be defined; however, some details can evolve with time. • There is a need to get a product to the market early. • A new technology is being used • Resources with needed skill set are not available • There are some high risk features and goals.
- 16. RAD model
- 17. RAD model Advantages •Reduced development time. •Increases reusability of components •Quick initial reviews occur •Encourages customer feedback •Integration from very beginning solves a lot of integration issues. Disadvantages •Depends on strong team and individual performances for identifying business requirements. •Only system that can be modularized can be built using RAD •Requires highly skilled developers/designers. •High dependency on modeling skills •Inapplicable to cheaper projects as cost of modeling and automated code generation is very high.
- 18. RAD model When to Use • RAD should be used when there is a need to create a system that can be modularized in 2-3 months of time. • It should be used if there’s high availability of designers for modeling and the budget is high enough to afford their cost along with the cost of automated code generating tools. • RAD SDLC model should be chosen only if resources with high business knowledge are available and there is a need to produce the system in a short span of time (2-3 months).
- 19. Agile model
- 20. Agile model Advantages •Customer satisfaction by rapid, continuous delivery of useful software. •People and interactions are emphasized rather than process and tools. Customers, developers and testers constantly interact with each other. •Working software is delivered frequently •Face-to-face conversation is the best form of communication. •Close, daily cooperation between business people and developers. •Continuous attention to technical excellence and good design. •Regular adaptation to changing circumstances. •Even late changes in requirements are welcomed Disadvantages •In case of some software deliverables, especially the large ones, it is difficult to assess the effort required at the beginning of the software development life cycle. •There is lack of emphasis on necessary designing and documentation. •The project can easily get taken off track if the customer representative is not clear what final outcome that they want. •Only senior programmers are capable of taking the kind of decisions required during the development process. Hence it has no place for newbie programmers, unless combined with experienced resources.
- 21. Agile model When to Use • When new changes are needed to be implemented. The freedom agile gives to change is very important. New changes can be implemented at very little cost because of the frequency of new increments that are produced. • To implement a new feature the developers need to lose only the work of a few days, or even only hours, to roll back and implement it. • This effectively gives the customer the finished system they want or need.
- 22. Iterative model
- 23. Iterative model Advantages •In iterative model we can only create a high-level design of the application before we actually begin to build the product and define the design solution for the entire product. Later on we can design and built a skeleton version of that, and then evolved the design based on what had been built. •In iterative model we are building and improving the product step by step. Hence we can track the defects at early stages. This avoids the downward flow of the defects. •In iterative model we can get the reliable user feedback. When presenting sketches and blueprints of the product to users for their feedback, we are effectively asking them to imagine how the product will work. •In iterative model less time is spent on documenting and more time is given for designing. Disadvantages •Each phase of an iteration is rigid with no overlaps •Costly system architecture or design issues may arise because not all requirements are gathered up front for the entire lifecycle
- 24. Iterative model When to Use • Requirements of the complete system are clearly defined and understood. • When the project is big. • Major requirements must be defined; however, some details can evolve with time.
- 25. Spiral model
- 26. Spiral model Advantages •High amount of risk analysis hence, avoidance of Risk is enhanced. •Good for large and mission-critical projects. •Strong approval and documentation control. •Additional Functionality can be added at a later date. •Software is produced early in the software life cycle Disadvantages •Can be a costly model to use. •Risk analysis requires highly specific expertise. •Project’s success is highly dependent on the risk analysis phase. •Doesn’t work well for smaller projects.
- 27. Spiral model When to Use • When costs and risk evaluation is important • For medium to high-risk projects • Long-term project commitment unwise because of potential changes to economic priorities • Users are unsure of their needs • Requirements are complex • New product line • Significant changes are expected (research and exploration)
- 28. Prototype model
- 29. Prototype model Advantages • Users are actively involved in the development • Since in this methodology a working model of the system is provided, the users get a better understanding of the system being developed. • Errors can be detected much earlier. • Quicker user feedback is available leading to better solutions. • Missing functionality can be identified easily • Confusing or difficult functions can be identified Requirements validation, Quick implementation of, incomplete, but functional, application. Disadvantages • Leads to implementing and then repairing way of building systems. • Practically, this methodology may increase the complexity of the system as scope of the system may expand beyond original plans. • Incomplete application may cause application not to be used as the full system was designed Incomplete or inadequate problem analysis.
- 30. Prototype model When to Use • Prototype model should be used when the desired system needs to have a lot of interaction with the end users. • Typically, online systems, web interfaces have a very high amount of interaction with end users, are best suited for Prototype model. It might take a while for a system to be built that allows ease of use and needs minimal training for the end user. • Prototyping ensures that the end users constantly work with the system and provide a feedback which is incorporated in the prototype to result in a useable system. They are excellent for designing good human computer interface systems.
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