Waterfall Model In Software Testing | What it is & Example?

The Waterfall Model is a widely used approach in software engineering that follows a sequential and linear process. It consists of distinct phases: planning, requirements gathering, system design, implementation, testing, and deployment. Each stage must be completed before moving on to the next.

While its limitations include limited flexibility and adaptability, it remains relevant today for projects with well-defined requirements and stable environments.

Let us dive in and learn more about the Waterfall Model in software testing.

What is Waterfall Model?

The Waterfall model is a methodical and step-by-step process of creating software from one stage to another. This approach requires completing each phase before the next phase can begin. The primary goal of the Waterfall model is to guarantee that all software requirements are met and that the software performs as anticipated. It offers a structured and logical approach to software creation that ensures high quality and efficiency throughout the development process.

Why Do We Use the Waterfall Model?

This model is used for the following purposes:

1. The Waterfall model is a well-organized and efficient approach to software development. 
2. This model ensures that all requirements related to a particular phase are met before moving on to the next phase, resulting in high quality and productivity. 
3. By adhering to this model, developers can ensure that all software development life cycle aspects are properly addressed.
4. This model leads to a more streamlined and organized final product. 
5. The Waterfall model is particularly suitable for software development projects requiring high precision and attention to detail.

Who Uses the Waterfall Model?

The Waterfall model was historically a widely used project management approach, especially in the early days of software development. The following are some examples of types of projects where the waterfall model is often used:

• Enterprise software: Enterprise software is typically complex and requires careful planning and execution. The waterfall model ensures that all requirements are met, and the software is delivered on time and within budget.

• Government software: Government software projects often have strict requirements and deadlines. The waterfall model ensures these requirements are met, and the software is delivered on time.

• Embedded systems: Embedded systems are typically small, specialized ones embedded in larger systems. The waterfall model can be used to ensure that these systems are developed correctly and meet all their requirements.

Despite its limitations, the waterfall model is still popular for software testing in many industries. It is a simple methodology that can be effective for projects with well-defined requirements and stable environments.

Even today, the Waterfall model is implemented by 51% of organizations. Companies like Toyota, IBM, Microsoft, etc., still use the waterfall model in software testing for various reasons. It includes its 

• simplicity, 
• effectiveness for large and complex projects, and 
• ability to help ensure all requirements are met.

Features of the Waterfall Model

The waterfall model is a widely used software development approach structured in a strict sequence of steps. 

1. One of the key features of the waterfall model is its emphasis on documentation, which is critical for achieving traceability and ensuring that the software meets the desired requirements.
2. Another important characteristic of the waterfall model is its strict adherence to a predefined schedule, which can help to ensure that the project is completed on time and within budget. 
3. The model features a clear, linear structure, enabling developers to track progress and identify potential issues early in development.
4. The waterfall model is a highly structured and disciplined approach to software development that is well-suited to projects with clear and well-defined requirements.

Advantages and Disadvantages of the Waterfall Model in Software Testing

The Waterfall Model in software testing has several advantages, including clear and well-defined project requirements, a sequential structure that allows for easy planning and scheduling, and easier management and control of project progress. It is most suitable for projects with stable and unchanging requirements, and its well-documented process makes it easier for new team members to join. 

However, the Waterfall Model in software testing also has several disadvantages. It needs to be more flexible in accommodating changes in requirements, limits client involvement during the development process, and has a high risk of project failure if initial requirements need to be corrected or completed. Also, it can be difficult to estimate accurate timelines and costs upfront, and testing is often left until the end, which can lead to late detection of issues. Therefore, the waterfall model is not widely used in software outsourcing to Latin America, Eastern Europe, and other tech hubs.

Example of Waterfall Model

Here’s an illustration of the waterfall model using the development of a mobile app for online grocery shopping:

Product: Online Grocery Shopping App
Requirements Gathering and Analysis Tasks: 

• Conduct user research to understand needs and pain points.
• Define app features and functionalities (e.g., product catalog, search, shopping cart, checkout, payment, delivery options, order tracking).
• Create user stories and use cases.

Develop a detailed requirements document outlining scope, functionality, and technical specifications.

Design Tasks:

• Create wireframes and mockups to visualize app layout and navigation.
• Design user interface (UI) elements, ensuring consistency and user-friendliness.
• Develop user experience (UX) flows for smooth interactions.
• Define technical architecture and system design for back-end integration.

Create a detailed design document for developers.

Implementation and Coding Tasks:

• Write actual code using chosen programming languages and frameworks.
• Integrate front-end (user interface) with back-end (database, servers).
• Develop APIs for communication with external services (e.g., payment gateways, delivery providers).

Implement security measures to protect user data.

Testing Tasks:

• Conduct unit testing to verify individual code components.
• Perform integration testing to ensure seamless interaction between modules.
• Carry out system testing to evaluate overall system behavior.
• Conduct user acceptance testing (UAT) with real users to gather feedback and identify issues.

Fix any bugs or defects found during testing.

Deployment Tasks: 

• Release the app to the app store or make it available for download.
• Configure servers and infrastructure for hosting and delivery.

Set up monitoring and maintenance processes.

Maintenance Tasks:

• Address bugs or issues reported by users.
• Release updates with new features or improvements.
• Perform regular maintenance and security checks.

Adapt the app to changing technologies and user needs.

The waterfall model could be more flexible. If changes are needed to the requirements after the development process has begun, it can be difficult and expensive to make those changes.

Different Phases of Waterfall Model in Software Engineering

The waterfall model is a traditional software development approach that follows a linear and sequential process. It consists of several distinct phases, each with its objectives and deliverables. 

Let’s explore each phase briefly:

1. Plan: The first phase, the Plan phase, sets the foundation for the entire project. During this phase, the project team defines the software product’s scope, objectives, and constraints. It involves gathering information about the client’s requirements, goals, and expectations, which serves as a basis for the subsequent phases.
2. Requirements: In this phase, the project team identifies and documents the client’s requirements, goals, and expectations for the software product.
3. Design: The system design phase begins once the requirements are gathered. It involves creating a high-level architectural design that outlines how different components of the software will interact with each other.
4. Implementation(coding): The implementation phase focuses on translating the system design into actual code. Developers write code based on the specifications provided during the previous phases. 
5. Testing: After implementation, thorough testing is conducted to identify any defects or errors in the software. This includes unit testing (testing individual components), integration testing (testing how different components work together), and system testing (testing the entire system). Automation testing plays a significant role. It helps us to achieve faster and more accurate results. Some famous tools are Testsigma, Selenium, and Apium.

6. Deployment:  Once all testing is complete, the software is ready for deployment, where it can be installed and used by end-users.
7. Maintenance:  During the maintenance phase, any necessary updates or bug fixes are implemented to ensure the software functions smoothly and efficiently.

When to Use SDLC Waterfall Model?

Here are some scenarios where the Waterfall Model can be effectively used:

1. Well-defined and stable requirements: The Waterfall Model is suitable when the project requirements are clear, unambiguous, and unlikely to change significantly during development. This model works best when there is little uncertainty or risk associated with the project.
2. Small-scale projects: The Waterfall Model is often used for small-scale projects with limited complexity. Since it follows a sequential approach, managing and controlling smaller projects is easier than larger ones.
3. Projects with fixed budgets and timelines: If a project has strict budgetary constraints or tight deadlines that cannot be altered, the Waterfall Model can be useful. Its linear nature allows for better estimating of the resources and time required for each phase.

How do you Test Software in Waterfall Development?

Testing in the Waterfall model follows a sequence and has a systematic approach. We can look at it here:

Requirement Phase:

Planning: Let’s come up with a test strategy and draft a high-level test plan that is aligned with the requirements. The plan should specify what will be tested, what resources are needed, and how testing will be approached.

Design Phase:

Test Case Design: Detailed test cases and test scenarios need to be developed based on the design documents. Every aspect of the design needs to be covered by these tests so that we can ensure they meet the specified requirements.

Implementation Stage:

Unit Testing: Check the accuracy of individual components or modules by performing unit tests. Developers typically conduct this test to detect any issues at an early stage of development.

Integration Testing: Following unit testing, combine the components together and examine how they interact with each other. This is done to confirm that all components work collectively as intended.

Verification Phase:

System Testing: Perform comprehensive testing of the entire system to ensure it meets the specified requirements. This includes functional testing, performance testing, security testing, and other types relevant to the system.

User Acceptance Testing (UAT): Validate the system with real users in a user-like environment to ensure it meets business needs and is ready for production.

Maintenance Phase:
Post Deployment Testing: Monitor the system in production for the purpose of detecting problems related to user interaction. This phase involves resolving bugs and making updates where needed.

How do We Ensure Quality and Testing in the Waterfall Model?

Here are some tips to make sure the quality and testing:

Establish specific quality standards and criteria 

Ensuring high-quality standards and effective testing is paramount in the Waterfall model to provide the software seamlessly aligns with defined requirements and functions. 

To achieve this, it is essential to establish specific quality standards and criteria before initiating the project. These criteria should encompass a range of aspects, including metrics, reviews, audits, and more.

Quality assurance at each phase:

Quality assurance must be incorporated at each phase of the Waterfall model, involving meticulous reviews, inspections, walkthroughs, and applying industry best practices and development guidelines. 

Thorough testing is important for any project. This involves creating and implementing test cases, using reliable tools and techniques for software testing.

Maintain a structured approach:

To maintain a structured approach, capturing and rectifying defects within each phase of the Waterfall model is vital. A robust defect management system, such as a bug-tracking tool, facilitates efficient defect documentation and resolution.

Continuous feedback and improvement:

Likewise, continuous feedback and improvement mechanisms should be in place at each phase of the Waterfall model. Feedback and quality improvement methods ensure development process refinement.

Waterfall Model and Tools

Some of the tools that enable following waterfall model during software development are:
1. The Gantt chart is an essential tool in the Waterfall Model, allowing project managers to visually plan and track the sequential phases of the project, ensuring efficient resource allocation and timely completion. 
2. Requirement traceability matrix helps maintain a clear link between the project requirements and their corresponding design, development, and testing activities, enabling effective change management and ensuring all requirements are met.

For example, let’s consider a software development project that aims to create an e-commerce website. The initial requirement states that the website should have a user registration feature. The waterfall model would use the Requirement Traceability Matrix (RTM) to maintain a clear link between this requirement and subsequent activities.
3. Documentation tools play a significant role in the Waterfall Model by capturing detailed project specifications, design documents, test plans, and user manuals, ensuring thorough documentation for future reference and maintenance.

For example, let’s consider a software development project following the waterfall model. In the initial phase of requirements gathering, the documentation tool is essential in capturing all the detailed project specifications. The team can use tools like Microsoft Word or Google Docs to create a complete requirements document that outlines all the functional and non-functional requirements of the software.

Once the requirements are documented, the design phase begins. Here, UML (Unified Modeling Language) modeling tools such as Enterprise Architect or Lucidchart can be utilized to create detailed design documents. These tools allow developers to visually represent system architecture, class diagrams, sequence diagrams, and other design elements necessary for building the software.

Test management tools like TestRail or JIRA can help create test plans and track test cases during the testing phase. These tools enable testers to document various test scenarios, expected and actual results for each test case. This ensures that all aspects of the software are thoroughly tested before moving on to the next stage.

4. Version control systems aid in managing different versions of software or code throughout the development process in the Waterfall Model, allowing developers to track changes, collaborate effectively, and maintain a reliable source code repository.
For example, let’s consider a software development project following the waterfall model. The team consists of multiple developers working on different software modules simultaneously. To ensure smooth collaboration and efficient management of code versions, they utilize a version control system (VCS) like Git. At the beginning of the project, the team sets up a central repository on a platform like GitHub or Bitbucket. Each developer creates a branch from the main branch to work on their module. This branching mechanism allows them to work independently without interfering with each other’s code.

They regularly commit changes to their branches in the VCS, providing detailed commit messages describing what modifications were made. This helps keep track of individual contributions and understand the codebase’s evolution.

Applications of Classical Waterfall Model

The classical waterfall model is widely used in software development projects with well-defined and stable requirements.

• It provides a structured approach to project management, ensuring that each phase of the development process is completed before moving on to the next.
• The model is beneficial for large-scale projects with a long duration, as it allows for better planning and resource allocation.
• It helps identify potential risks and issues early in the development cycle, allowing for timely mitigation strategies.
• The waterfall model promotes documentation at each stage, which aids in maintaining a clear understanding of the project’s progress and requirements.
• It facilitates better stakeholder communication by providing a clear framework for discussing project milestones and deliverables.
• The model suits projects with strict regulatory or compliance requirements, ensuring that all necessary steps are followed and documented.
• It can be beneficial when working with clients who prefer a linear and predictable development process, as it provides a clear timeline of deliverables.
• Also, the model promotes accountability and transparency among team members, fostering a collaborative and efficient work environment.

Alternatives to the Waterfall Model

A number of alternative models have been developed to overcome the limitations of the Waterfall model. Let’s take a look at some widely used alternatives:

Agile Model:

In Agile model, Testing is done hand-in-hand with development. The entire development in Agile is split into sprints, each involving Testing of the incrementally developed features. Constant feedback and adaptation facilitate early identification and rectification of problems.

Iterative Model:

This model used for Testing is based on the development of a project in iterations. Each iteration consists of design, implementation and Testing, where the system takes shape and develops properly with each cycle.

Spiral Model:

The Spiral model combines iterative development with risk analysis. Testing is part of each spiral or phase, with prototypes being tested early and often to address risks and gather user feedback.

V-Model (Verification and Validation Model):

This method ensures verification and validation throughout the entire project. Each of these stages must be followed by a corresponding testing phase. For example, acceptance testing is paired with requirements analysis, and integration testing is paired with design.

DevOps:

The method concentrates on continuous integration and continuous delivery (CI/CD). The test is automated and tied to the development process, which makes it possible to quickly check any changes in the code during the production cycle.

Takeaway

Here we are, ready to wrap things up! 

The Waterfall model is a linear and structured software development and testing methodology that provides an easy-to-follow path of sequential steps. Although it does provide predictability and extensive documentation, it is very inflexible when it comes to dynamic environment changes. Being aware of what it can and cannot do allows teams to make an informed choice about whether or not this is the right methodology for them.

Frequently Asked Questions

What is the difference between Waterfall Model and Agile Model?

The Waterfall Model is a linear and sequential approach to software development, where each phase is completed before moving on to the next. In contrast, the Agile Model is an iterative and flexible approach emphasizing collaboration and adaptability throughout development. Agile allows for frequent feedback and adjustments, while Waterfall follows a predetermined plan with limited room for changes.

Is Waterfall better than Agile?

The waterfall model is more appropriate for projects with fixed requirements and where the steps are supposed to be sequential; in contrast, Agile is better suited for environments demanding adaptability and feedback loops throughout the process. The decision to adopt one over the other should be informed by an understanding of the project’s specific needs and end objectives.

What is the SDLC Waterfall Model?

The Waterfall Model follows a software development life cycle (SDLC) that proceeds through different phases — requirements, design, implementation, testing, deployment, and maintenance — in a specific order without overlap. The idea is to take a systematic, step-by-step approach to software engineering to maintain control throughout each phase of the project.