What best describes tests run in an isolated environment?

• A. Tests run with minimal side effects from other tests.
• B. Tests share global state.
• C. Tests require the entire system to be running.
• D. Tests rely on external networks.

Answer: (A)

Tests run in an isolated environment prioritize a clean starting point and no cross-test influence. The goal is for each test to operate with its own separate state and without depending on or altering the state of other tests or parts of the system. This makes results deterministic and reproducible, because a test isn’t affected by or capable of affecting shared data from other tests.

That’s why the best description is that tests run with minimal side effects from other tests. They avoid shared global state, unnecessary external dependencies, and full-system requirements, so each test stands alone. In contrast, sharing global state invites interference between tests, requiring the entire system or external networks introduces complexity and nondeterminism, and leaning on external networks makes tests flaky and less reproducible.