pub fn with_test_observer<F, R>(observer: Arc<dyn Observer>, f: F) -> Rwhere
F: FnOnce() -> R,Expand description
Test-flavored helper. Installs the observer per-thread for the
duration of f; restores on closure exit. Used by #[obs::test]
(Phase 2 task 2.6) and by users that want to assert what was
emitted from a synchronous block.
Takes Arc<dyn Observer> so the caller can keep a clone and
inspect it after the closure (e.g. InMemoryObserver::handle()).
Spec 11 § 3.1.
Nested calls stack LIFO via the per-thread RefCell slot.