Epic: Explicit test requirements #395

Scenarios that need something the environment does not provide, such as a PHP extension, a database type or an external tool, should never cost a run and never disappear unnoticed.

They should either be filtered out up front with a clear report of what was not tested and why, or stop the run before it starts when the environment is expected to be complete, as on CI. A scenario failing halfway through because a tool is missing wastes compute and hides the actual cause.