refusal property
Refusal says why the run proves nothing, when it does. An empty history is REFUSED rather than reported as zero alerts: "no alerts" is exactly what a quiet model looks like, and choosing a shape on the strength of an empty replay is the failure a sandbox exists to prevent.
Please note: This property should have been non-nullable! Since the specification file does not include a default value (using the "default:" property), however, the generated source code must fall back to having a nullable type. Consider adding a "default:" property in the specification file to hide this note.
Implementation
String? refusal;