Development, Validation, Testing

The Development, Validation, and Testing phase is where the actual software comes to life.

After the requirements have been gathered and the system has been designed, developers begin writing code and implementing features. This phase is often the most cyclical of the entire Software Development Lifecycle (SDLC), with developers and testers working in close feedback loops.

Unlike earlier phases, which are more about planning and design, this stage is about building and proving.

Development: Programmers translate the system design into working code. This may involve writing new modules, integrating libraries, or extending existing systems. Development can happen in short iterations (Agile) or in longer, predefined cycles (Plan-driven).

Validation: As the code is written, developers and testers confirm that the work meets both the system design and the original requirements. Validation answers the question: "Are we building the right system?"

Testing: Testing ensures the software works correctly and reliably. There are many different types of testing, some of which include:

  • Unit testing (testing small pieces of code in isolation).
  • Integration testing (checking how components interact).
  • End-to-end Testing (verifying the whole system against requirements).

Because development will introduce bugs and unexpected behaviour, development and testing repeats in cycles until the system that is being worked on is stable and meets its goals.

Check Your Understanding

  1. Why is this phase considered the most cyclical phase of the SDLC?
  2. What is the difference between Validation and Testing?
  3. How might development look different in a Plan-Driven methodology vs. an Agile one?