Software testing waterfall model
This year we have spent quite a bit of time looking at various testing approaches and methodologies. This week, we continue in that vein by looking at the software testing waterfall model. We’ll break it down for you and describe why you might use it, then listing the advantages and disadvantages.
What is the waterfall model?
The waterfall model is popular in software engineering and product development. Indeed, it is often cited as the first software development methodology. Essentially, it is an approach to the software development lifecycle (SDLC) that uses a logical progression of steps / phases for a project. Goals are set for each phase of development which cannot be revisited once completed. This is because in the waterfall model, each phase is dependent on the output of the previous one. The model works well as a high-level project management methodology and can be used in many different contexts. The linear progression incorporated makes the approach particularly popular on complex projects.
Why use the waterfall model in software testing?
Whilst other development methodologies include a project’s end user or client in the phases of a project, the waterfall model does not. Instead, users are consulted during the initial requirements stages. Client feedback is then sought after that. By operating in this manner, development teams can move through project phases more rapidly. This is particularly good for projects where fixed requirements are set at the beginning. Other typical characteristics of the waterfall model are:
- Projects have a high degree of process definition
- There is little or no output variability
- Waterfall projects are predictable and have specific documentation
- There are fixed requirements and an established timeline
Waterfall is particularly useful in software development when an application needs to work on the first attempt because that is the objective. By contrast, ‘Agile’ methodologies are iterative. They use repeated cycles that build upon each other involving designing, developing and testing software.
Waterfall model phases
In the software development process, waterfall models are typically made up of the following stages:
- Requirement analysis
- System design
Before moving on to the next phase in the waterfall model, a review and sign off process takes place. This ensures that the defined goals have been met. For example, developers would ensure each unit of technology is properly integrated in the implementation phase before moving on to testing.
A critical phase in which requirements for the software product to be developed are gathered and analysed. The objective is to gain an understanding of the customer’s requirements so they can then be translated into functional and technical specifications for the development team. The requirement analysis phase is critical in the waterfall model because it ‘sets the stage’ for the whole project.
The next phase sees the aforementioned translation taking place as a detailed technical design is created. Another crucial phase, it sets the technical direction for the development team. It ensures that stakeholder requirements will be met by the system as well as providing a detailed plan for building the system.
In this phase, the system design plan is used to develop and code the software product. Development teams perform actions including coding, testing, and debugging to ensure that the software product is functional. The implementation phase is also critical in this model, because it is the phase where the actual software product is developed.
The Testing phase sees the software product tested to identify defects, errors and any other issues. As with the other phases, ensuring that it meets the requirements and specifications originally defined is critical. The testing phase involves various activities such as planning, designing, executing, and reporting.
Once the software product has passed the testing phase, it is then released and deployed to end-users. The primary goal of the deployment phase is to ensure that it is functioning correctly.
This phase in the waterfall model sees the software product maintained and updated to ensure that it continues to meet the changing needs of end-users or clients.
The waterfall model: Advantages / disadvantages
- It is a well-structured and straightforward model
- Objectives are clearly defined
- The model is easy to understand and to then communicate to stakeholders
- There is a high level of control over the development process, making it easier to manage risks and control project scope
- There is a lack of flexibility
- The model has a high risk of project failure if any of the phases encounter issues
- Feedback is delayed until the testing phase, which can make it difficult to identify and address issues until later in the development process
- It offers limited collaboration
The software testing waterfall model is a well-structured and straightforward model. It provides a high level of control over the development process but is not without its drawbacks. A lack of flexibility plus delayed feedback and limited collaboration mean you must decide when to deploy it wisely.