connectionFactoryForTest property
Test-only seam (BEH-12): overrides how the InternetConnection is
constructed in _initializeNetworkChecking so the leak/idempotency test
(BEH-3) can inject a fake that records dispose()/subscription lifecycle.
When null, the real InternetConnection.createInstance is used.
Implementation
@visibleForTesting
InternetConnection Function(String primaryUrl)? connectionFactoryForTest;