@SuppressWarnings("unchecked")
    public void injectStages(Object stage) {
        for (Field field : FieldCache.get(stage.getClass()).getFieldsWithAnnotation(ScenarioStage.class)) {
            Object steps = addStage(field.getType());
            ReflectionUtil.setField(field, stage, steps, ", annotated with @ScenarioStage");
        }
    }
Initialize the fields annotated with {@link ScenarioStage} in the test class.
jgiven-core/src/main/java/com/tngtech/jgiven/impl/ScenarioExecutor.java