What is a V-shaped model in the context of software development?

The V-model is a software development methodology that extends the waterfall model. It emphasizes the relationship between development phases and testing phases at each level of abstraction. The model has a V shape, where the left side represents development phases (descending path), and the right side represents corresponding testing phases (ascending path).

V-model phases:

Left side (Development):

1. Requirements analysis: Define and document user and system requirements.
2. System design: High-level architecture design.
3. Architectural design: Detailing system architecture, defining modules and their interactions.
4. Module design: Detailed design of each module or component.
5. Coding: Writing code according to design documents.

Right side (Testing and verification/validation):

1. Unit testing: Testing each module independently. Corresponds to Implementation phase. Goal: verify correctness of individual components.
2. Integration testing: Testing interaction between integrated modules. Corresponds to Module Design and System Design phases. Goal: verify correct interaction.
3. System testing: Testing the entire integrated system against system requirements. Corresponds to System Design phase. Goal: verify compliance with functional and non-functional requirements.
4. Acceptance testing: End-user or customer testing. Corresponds to Requirements analysis phase. Goal: verify system meets business needs and user expectations.

Advantages:

• Focus on early testing.
• Clear correspondence between development and testing phases.
• Improved verification and validation.
• Easy to understand and apply.

Disadvantages:

• Less flexible than iterative models.
• Not suitable for projects with changing requirements.
• Labor-intensive, especially for small projects.
• Does not consider iterative development and Agile methodologies.

The V-model is suitable for projects with stable and well-defined requirements, where the risk of requirement changes is low.