Iterative Model

What is the Iterative Model?

The Iterative Model starts development with a simple implementation of a small set of requirements, then iteratively refines it through a series of repeating cycles, adding new functionality and improving the design with each pass, until the complete system is built. Unlike the Incremental Model, which adds complete features, the Iterative Model evolves the entire system incrementally.

The Iterative Development Cycle

• Initial Planning: A basic set of requirements is understood, and initial planning for the first iteration is done.
• Requirements of the Iteration: Requirements to be covered in the current iteration are finalised.
• Analysis & Design: The design is updated to accommodate new requirements for this cycle.
• Implementation & Testing: The iteration's functionality is coded and tested.
• Evaluation: The iteration is reviewed against objectives, and the next cycle is planned based on lessons learned.

Advantages of the Iterative Model

• Working versions of the software are produced early and often.
• Easier to test and manage risk since problems are found in smaller, isolated iterations.
• Progress can be measured more easily since each cycle is a milestone.
• Feedback from one iteration directly improves the next.

Disadvantages of the Iterative Model

• Requires more management attention to keep iterations aligned with overall goals.
• Since not all requirements are gathered upfront, the final architecture can need rework.
• Costs can be harder to predict since the total number of iterations may be unclear.
• Risk analysis in each iteration requires experienced resources.

When Should Testers Use the Iterative Model?

• Large systems where it's easier to find requirements through repeated cycles.
• Projects where the core architecture is understood but detailed features can evolve.
• When early, partial delivery of working software is valuable to stakeholders.

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