public class DroolsScoreDirector ... { // class in OptaPlanner

    private final boolean generateDroolsUnitTest = false; // New flag

    protected KieSession kieSession;
    ...

       public Score calculateScore() {
        variableListenerSupport.assertNotificationQueuesAreEmpty();
        if (generateDroolsUnitTest) {
            System.out.println("kieSession.fireAllRules();");
        }
        kieSession.fireAllRules();
        ...
    }

    private void update(Object entity) {
        if (generateDroolsUnitTest) {
            System.out.println("FactHandle factHandle = kieSession.getFactHandle(" + entity + ");");
            System.out.println("kieSession.update(factHandle, " + entity + ");");
        }
        FactHandle factHandle = kieSession.getFactHandle(entity);
        ...
        kieSession.update(factHandle, entity);
    }

    @Override
    public void afterVariableChanged(VariableDescriptor variableDescriptor, Object entity) {
        System.out.println(entity + ".set"+ variableDescriptor.getVariableName().makeFirstCharCapital() + "(" + variableDescriptor.getValue(entity) + ");");
        update(entity);
        super.afterVariableChanged(variableDescriptor, entity);
    }

}