Waterfall Model

What is the Waterfall Model?

The Waterfall Model is the oldest and most straightforward SDLC model. It follows a strict, linear sequence where each phase must be completed before the next one begins — like water flowing downwards over a series of steps, it never goes back up. This model is simple and easy to understand, making it a popular choice for projects with stable requirements.

Phases of the Waterfall Model

• Requirement Analysis: All possible requirements of the system are gathered and documented before any design work starts. This phase produces a Software Requirements Specification (SRS).
• System Design: Requirements are studied and the system architecture is prepared. This includes high‑level design (module structure) and low‑level design (detailed component specifications).
• Implementation (Coding): The system is developed in small programs called units, which are later integrated. Code is written according to the design documents.
• Integration & Testing: All units are integrated and tested to ensure the entire system works as expected. This is the first time the software is executed.
• Deployment: The product is deployed in the customer environment or released to the market.
• Maintenance: Issues found in the live environment are fixed, and enhancements are released as patches or new versions.

Advantages of the Waterfall Model

• Simple, easy to understand and use because of its linear, sequential flow.
• Each phase has clearly defined deliverables, making it easy to manage and measure progress.
• Well suited to projects where requirements are well understood and unlikely to change.
• Documentation produced at every stage makes it easier to onboard new team members.

Disadvantages of the Waterfall Model

• Testing starts only after development is complete, so bugs surface very late.
• Very difficult and expensive to go back and change something once a phase is finished.
• Not suitable for complex, long‑running or object‑oriented projects.
• Poor fit when requirements are unclear or expected to evolve.

When Should Testers Use the Waterfall Model?

• Small projects with clear, fixed and well‑documented requirements.
• Projects where the technology being used is well understood by the team.
• Situations where ample resources with the required expertise are available.

Understanding when — and when not — to apply the Waterfall Model helps testers plan the right test strategy and align testing effort with how the project is actually being built.