Waterfall Model
The Waterfall model is a sequential and linear SDLC approach where each phase is completed in order. Progress flows downward like a waterfall.
1. Definition
The Waterfall Model is a sequential and linear SDLC model where each phase is completed one after another, and the next phase starts only after the previous phase is finished.
- Progress flows downward like a waterfall.
2. Phases of the Waterfall Model
- Requirement Analysis
- System Design
- Development
- Testing
- Deployment
- Maintenance
Each phase has clearly defined deliverables and sign-off.
3. Key Characteristics
- Strict phase-by-phase execution
- Heavy documentation
- Minimal customer involvement after requirements
- Changes are difficult and costly
- Testing happens late in the cycle
4. Role of Manual Tester in Waterfall
Requirement Phase
- Review requirement documents
- Identify ambiguities and missing scenarios
- Understand complete system behavior
Design Phase
- Review design documents
- Prepare high-level test scenarios
Development Phase
- Prepare detailed test cases
- Review test cases
Testing Phase
- Execute test cases
- Log defects
- Perform re-testing and regression testing
5. Advantages of Waterfall Model
- Simple and easy to understand
- Clear milestones and documentation
- Well-suited for stable requirements
- Easy project tracking
6. Disadvantages of Waterfall Model
- Late testing → late defect detection
- High cost of change
- Limited flexibility
- No early working software
7. When Waterfall Is Suitable
- Requirements are fixed and well-defined
- Regulatory or compliance-heavy projects
- Short, low-risk projects
- Legacy systems
8. Real-Time Example
Banking core systems or government applications often follow Waterfall due to strict documentation and approval requirements.
9. Waterfall Model vs Agile (High-Level)
| Aspect | Waterfall | Agile |
|---|---|---|
| Flow | Sequential | Iterative |
| Testing | Late phase | Continuous |
| Flexibility | Low | High |
| Documentation | Heavy | Light |
10. Common Mistakes
- Assuming no testing until testing phase
- Ignoring early requirement reviews
- Underestimating testing time
11. Interview-Ready Answers
Short answer:
The Waterfall model is a linear SDLC model where each phase is completed fully before moving to the next phase.
Detailed answer:
Waterfall is a sequential development model with clearly defined phases, heavy documentation, and testing performed after development, making it suitable for projects with stable requirements.
12. Key Takeaway
Waterfall works best when requirements are stable, but late testing increases defect risk and cost.