crashed with 'j.u.NoSuchElementException: No attribute named 'notStartedRefIds' is defined'

Question

I am working with Gatling and have received this error which occurs claiming 'notStartedRefIds' is defined. I am new to Gatling and am confident that the value has been declared properly already, however I cannot see why it is not being recognised.

The code which contains reference to the value is below:

case object StudentAssignmentScenario {

  private val notStartedRefIdsSession = "notStartedRefIds"

  private val studentAssignmentRefIdSession = "studentAssignmentRefId"

  private val endpoint: String = environmentAssignmentsUrls + "/v2/studentAssignments"

  private val startAssignment = http("Start StudentAssignment")
    .put(endpoint + "/${studentAssignmentRefId}/start")
    .headers(getHeaderMap)
    .check(status.is(200))


  private val submitAssignment = http("Submit StudentAssignment")
    .put(endpoint + "/${studentAssignmentRefId}/submit")
    .headers(getHeaderMap)
    .check(status.is(200))

  private val startAndSubmitAssignments = exec { session =>
    val refId = session(notStartedRefIdsSession).as[Seq[String]].apply(0)
    session.set(studentAssignmentRefIdSession, refId)
  }.exec(startAssignment).exec(submitAssignment)

  private val startAssignments = exec { session =>
    val refId = session(notStartedRefIdsSession).as[Seq[String]].apply(1)
    session.set(studentAssignmentRefIdSession, refId)
  }.exec(startAssignment)

  def readStudentAssignments = exec(http("Get Not Started StudentAssignments")
    .get(endpoint)
    .headers(getHeaderMap)
    .queryParamMap(Map[String, String]("inclExpired" -> "true",
      "context" -> "basel",
      "sort" -> "dueDate,title",
      "limit" -> "25", "offset" -> "0",
      "status" -> "NOT_STARTED"))
    .check(status.is(200),
      // save refIds
      jsonPath("$.items[?(@.status == 'NOT_STARTED')].refId").findAll.optional.saveAs("notStartedRefIds")))

  private val studentAssignmentWorkflow = exec(startAndSubmitAssignments)
    .exec(startAssignments)

  val studentAssignmentWorkflowSetup: ChainBuilder = exitBlockOnFail(
    group("Student Assignment Workflow") {
      studentAssignmentWorkflow
    })
}

Answer 1

The only place you seem to be populating notStartedRefIds is in readStudentAssignments where you extract it from the response thanks to a jsonPath.

However, you've configured this check as optional meaning you expect it to sometimes not be here. If that's the case, it's not surprise it can be undefined when calling session(notStartedRefIdsSession).