private void performInitialization() {
        if( modelBuilder == null ) {
            throw new IllegalStateException( "modelBuilder must be set before Scenario can be initalized." );
        }
        if( !initialized ) {
            executor.setListener( modelBuilder );
            initialize();
            initialized = true;
        }
    }
Finishes the scenario.

@throws Throwable in case some exception has been thrown during the execution of the scenario
jgiven-core/src/main/java/com/tngtech/jgiven/impl/ScenarioBase.java