Merging the Waterfall and Agile Approaches in a Hybrid Model
Traditionally, the Waterfall Model is the go-to approach for software development. This model adopts a sequential process that flows through the stages of Initiation, Analysis, Implementation, Testing, and Maintenance, ultimately transforming a concept into viable software.
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Yet, the Waterfall model comes with its share of drawbacks.
Then emerged Agile software development, aimed at circumventing the limitations of the Waterfall model. It introduced an alternate framework that deployed an incremental method rather than a sequential one.
Clients transitioning from the Waterfall model to Agile often experienced multiple issues due to the challenges of adapting to this novel software development strategy. Consequently, the final product often ended up being faulty.
This led to the creation of a new approach called the ‘Hybrid’ model. The hybrid model fuses the strengths of both Agile and Waterfall models to guarantee the rollout of a strong end product.
Firstly, we’ll discuss the Waterfall and Agile development models, and subsequently delve into the “Agile Waterfall Hybrid Model”, along with its respective strengths and weaknesses.
You Will Learn About:
Waterfall Model
The Waterfall model is a strategy for software development that section off a project into distinct stages. Each phase must be finished and evaluated before proceeding to the next.
In the Waterfall model, the stages follow a linear sequence with no overlap.
=> More information about the Waterfall Model can be found here.
This graphic offers a depiction of the Waterfall model:
Strengths of the Waterfall Model:
- Clear and simple to comprehend and use.
- Fixed model – Individual phases come with defined deliverables and review processes.
- Painstakingly maintains documentation and artifacts.
- Fits well for projects with easily-understood requirements.
Shortcomings of the Waterfall Model:
- Doesn’t fit for projects with changing requirements.
- Dealing with defects noted late in the project can be expensive.
- Not suitable for complex and lengthy projects.
- No operational software is developed until the project’s later stages.
Agile Model
According to Wikipedia, the Agile Model is “a collection of software development procedures based on iterative and incremental development, where requirements and solutions evolve via collaboration between self-organizing, cross-functional groups.”
This model prioritizes principles that favour interaction and cooperation over rigid processes.
=> For more articles about Agile methodology, click here.
(Enlarge image by clicking on it)
Strengths of the Agile Model:
- Customer involvement in the developmental process.
- The delivery of working software frequently leads to a high return on investment.
- Accommodates shifting requirements with ease.
- Encourages constant upgrades of both the product and the process.
Shortcomings of the Agile Model:
- Less emphasis on design and documentation.
- Needs a solid and proficient team.
Hybrid (Collaborative) Model
The Collaborative Model aspires to merge the strengths of both Waterfall and Agile methodologies. By capitalizing on the strengths of both models, the Collaborative Model guarantees the success of the project while limiting the drawbacks associated with each separate model.
The following steps can implement the Collaborative Model in a project:
Here is a visual representation of the Collaborative Model:
Strengths of the Hybrid Model:
- Fuses the advantages of both Agile and Waterfall methods.
- Enables the initial high-level design based on Waterfall principles.
- Allows for coding and testing using Agile methodology.
Agile Waterfall Hybrid Model – Learning by Example: A Case Study
The software company ‘ABC Software Service’ offers services to ‘XYZ University,’ a university that requires software development, testing, and maintenance.
Main features of the project are:
- ABC Software Services are tasked with upgrading XYZ University’s applications, including database upgrades and redevelopment of all applications using the latest available technology.
- Previously, all projects managed by ABC Software Services followed the Waterfall method.
- ‘Online registrations’ and ‘Online examinations,’ two highly prioritized applications with heavy traffic, have been scheduled for redevelopment.
- XYZ University insists that these applications be developed using the Agile model of software development.
The first project, ‘Online registrations,’ was implemented using the Agile method, but several weaknesses were identified in the processes followed. These flaws were deemed to be significant and were taken into account when executing the second project, ‘Online examinations,’ which was conducted using a Hybrid approach.
Reduction of Waterfall and Agile Development Techniques’ Shortcomings via a Hybrid Model:
Let’s delve into the specifics of these measures:
#1. Inadequate Documentation:
One of the Agile principles highlights the importance of “Working Software over Comprehensive Documentation.” Although Agile promotes a focus on delivering functional software, the diminished emphasis on documentation can become a long-term obstacle, particularly for projects like those of XYZ University, which require dedicated support squads to handle live projects and manage defects.
As opposed to Agile’s approach, the Waterfall model lays great stress on in-depth documentation, encompassing solution design, technical design, and walkthrough documents. These documents are the keys to smooth transitions and successful support. The non-availability of such documents for the ‘Online registrations’ project led to difficulties in addressing end-user tickets. There were no reference documents for the support team to rely on.
This experience served as a valuable lesson, and the ‘Online examinations’ project saw the development and transition of robust documentation to the support team.
=> Click here to understand the importance of documentation.
#2. Absence of UAT/End-to-end Testing:
In Agile software development, testers work with incremental builds and conduct regression testing as new builds are incorporated. However, comprehensive end-to-end testing of the final build in a new environment is critical after all sprints and integrations are complete.
=> Discover more about end-to-end testing in live projects.
The ‘Online registrations’ project was tested solely in the testing environment, and post system testing and defect resolution, it was considered ready for launch without conducting a second cycle of system testing or UAT. In contrast, the ‘Online examinations’ project went through SIT (System Integration Testing) before being transported to a UAT environment for the second testing cycle. This resulted in the identification and resolution of high-priority defects, ensuring a stable build before going live.
#3. Lack of a Dedicated Scrum Master:
The Scrum Master’s role is pivotal in ensuring adherence to Scrum values and practices. The Scrum Master functions as a coach, guiding the team to deliver their best efforts and ensuring efficient processes. During the ‘Online registrations’ project, the team operated without a dedicated Scrum Master, leading to unresolved issues and missed deadlines. However, the ‘Online examinations’ project involved a dedicated Scrum Master, who addressed project issues, prepared project sprint reports, and facilitated sprint planning and retrospective meetings. This improved the overall team performance and enabled team members to focus on their tasks while the Scrum Master handled other responsibilities.
#4. Transforming Project Documents into the Product Backlog:
Waterfall projects generally produce documents like Business Requirement Specifications (BRS), high-level design, and functional design. To execute coding, testing, and implementation phases in an Agile model, these project documents need to be converted into a product backlog.
The product backlog acts as the basis for an Agile project, ranking requirements, and functioning as a growable document based on customer feedback and changing requirements. The significant task of converting waterfall project documents to a product backlog demands a consensus among the entire team and stakeholders.
Once all the requirements are listed and the customer agrees to them, prioritizing these requirements is vital for sprint planning.
#5. Traceability Matrix:
Another significant artifact, commonly used in Waterfall projects, is the traceability matrix. To ensure no requirements are overlooked, a traceability matrix should be designed and maintained in a manner parallel to the product backlog. The traceability matrix helps map requirements to the executed test cases during user acceptance testing and end-to-end testing. It enables easy inclusion of omitted requirements, thanks to the flexibility and adaptability of the Agile methodology.
After the ‘Online registrations’ project went live, end users faced numerous issues, leading to a significant number of tickets being raised to the production support team. While many issues were resolved, additional change requests and improvements were made in subsequent releases to stabilize the application and enhance the end-user experience. As a result, the project costs spiraled upwards. To avoid overshooting the budget, meticulous planning and effective transitioning of projects to Agile are crucial. Each project requires a specially designed hybrid model that suits its individual needs.
Before initiating the ‘Online examinations’ project, meticulous attention was paid to the planning phase. A hybrid model was devised, with the requirements analysis and high-level design phases adhering to the Waterfall model, while the remaining stages adopted Agile principles.
The following is a visual representation of the adopted hybrid model:
Conclusion
It is clear that each of the Waterfall model and Agile model has its own set of shortcomings. Therefore, the adoption of a Hybrid model that leverages the strengths of both methodologies presents a practical solution. Success in any project hinges on the careful choice of the suitable model, which necessitates meticulous planning and consideration of factors like budget, time, resource utilization, and the complexity of requirements.
Even though the Agile manifesto espouses individual worth, operational software, customer cooperation, and adaptability, the Hybrid model acknowledges the significance of all aspects. Clients and project managers must evaluate the relative significance of each aspect for their individual projects.
About the author: This guest article was penned by Harshpal Singh, a QA Team Lead with over seven years of experience in manual, database, automation, and performance testing. He has worked on numerous projects that have employed the Waterfall, Agile, and Hybrid development models.
Have you had experience with a Hybrid model for development and testing? Share your experiences in the comments below.