Final answer:
Behavior-Driven Development (BDD) is the term for a system design and validation practice that emphasizes collaboration and uses test-first principles along with English-like scripts for clarity and behavioral validation.
Step-by-step explanation:
The term for a system design and validation practice that uses test-first principles and English-like scripts is Behavior-Driven Development (BDD). In Behavior-Driven Development, developers, testers, and non-technical stakeholders like business analysts collaborate using a shared set of tools and practices to describe and validate the desired behavior of the system. BDD focuses on obtaining a clear understanding of desired software behavior through discussion with stakeholders and uses that understanding to drive development with tests written in English-like language.
In the context of system design, a team might engage in activities such as prototyping, testing, and refinement. Testing of prototypes is a crucial step that may unveil new aspects of the system design, informing further iterations and refinements. BDD provides a structured approach to these practices by starting with the expected behavior which becomes the basis for test cases that guide development.