What term is used to describe isolated environments for testing applications and services?

The term used to describe isolated environments specifically set up for testing applications and services is indeed "testing environments." These environments are crucial in the software development lifecycle as they allow developers and testers to validate the functionality, performance, and security of applications without affecting live or production systems.

Testing environments are tailored to mimic the production environment as closely as possible, allowing for comprehensive testing scenarios. They are essential for quality assurance, enabling teams to identify and fix bugs before new features or updates are deployed to the production environment.

In contrast, production environments are where applications run live and serve end-users. Staging environments serve as a last step before production, acting as a replica for the final tests but not primarily for the testing of individual applications. Development environments are where initial coding and development take place, often incorporating unfinished code that may not be stable or fully functional yet.

Thus, the correct answer reflects the environment explicitly intended for rigorous testing and validation of applications, making it easier to assess their readiness for production deployment.