Replace field values of a nested object dynamically

I am trying to write integration test for my scala application(with akka-http). I am running into a problem, for which I am not able to find a solution.

My Case classes are as below:

case class Employee(id:Long, name:String, departmentId:Long, createdDate:Timestamp) extends BaseEntity
case class EmployeeContainer(employee:Employee, department:Department)  extends BaseEntity

I have a method like this

trait BaseTrait[E<:BaseEntity, C <: BaseEntity]{
    def getById(id:Long): Future[List[C]] = {
       //query from db and return result.
    }

    def save(obj:E) = {
      //set the createDate field to the current timestamp
      //insert into database
    }

}

I can extend my class with BaseTrait and just override the getById() method. Rest of the layers are provided by our internal framework.

class MyDao extends BaseTrait[Employee, EmployeeContainer] {
  override def getById(id:Long) = {
      for {
      val emp <- getFromDb(id)
      val dept <- DeptDao.getFromDb(emp.departmentId)
      val container = EmployeeContainer(emp,dept)
      } yield(container)
   }
}

So in the rest layer, I will be getting the response as the EmployeeContainer. The problem now I am facing is that, the modified date is automaticaally updated with the current timestamp. So, when I get back the result, the timestamp in the object I passed to save() method will be overwritten with the current time. When I write the test case, I need to have an object to compare to. But the timestamp of that object and the one I get abck will never be the same.

Is there anyway, in which I can replace all the occurrance of createDate with a known value of timestamp so that I can compare it in my testcase? The main problem is that I can not predict the structure of the container (it can have multiple case classes(nested or flat) with or without createDate fields).

I was able to replace the field using reflection if it comes in the main case class, but unable to do for nested structures.