result.txt

[info] ObjectIdExtractSpec:
[info] Extract
[info] - should return same ObjectId if I don't have an implicit ObjectIdStringSerializer in scope and pass format directly *** FAILED ***
[info]   57b5ba2c21e60e8ef31e77a0 was not equal to "57b5b4a321e65efe0b7b5fd5" (ObjectIdExtractSpec.scala:15)
[info] - should return same ObjectId if I don't have an implicit ObjectIdStringSerializer in scope *** FAILED ***
[info]   57b5ba2c21e60e8ef31e77a1 was not equal to "57b5b4a321e65efe0b7b5fd5" (ObjectIdExtractSpec.scala:21)
[info] - should return same ObjectId if I do have an implicit ObjectIdStringSerializer in scope
[info] Run completed in 310 milliseconds.
[info] Total number of tests run: 3
[info] Suites: completed 1, aborted 0
[info] Tests: succeeded 1, failed 2, canceled 0, ignored 0, pending 0
[info] *** 2 TESTS FAILED ***

Serializer.scala

class ObjectIdStringSerializer extends Serializer[ObjectId] {
  private val ObjectIdClass = classOf[ObjectId]

  def deserialize(implicit format: Formats): PartialFunction[(TypeInfo, JValue), ObjectId] = {
    case (TypeInfo(ObjectIdClass, _), json) => json match {
      case JString(s) if (ObjectId.isValid(s)) =>
        new ObjectId(s)
      case x => throw new MappingException("Can't convert " + x + " to ObjectId")
    }
  }

  def serialize(implicit formats: Formats): PartialFunction[Any, JValue] = {
    case x: ObjectId => JString(x.toString)
  }
}

test.scala

package code

import code.lib.ObjectIdStringSerializer
import code.testkit._
import net.liftweb.json._
import org.scalatest.Inspectors

import scala.reflect.Manifest

class ObjectIdExtractSpec extends BaseWordSpec with Inspectors  {
  "Extract" should {
    "return same ObjectId if I don't have an implicit ObjectIdStringSerializer in scope and pass format directly" in {
      val format = DefaultFormats
      val j = JString("57b5b4a321e65efe0b7b5fd5")
      Extraction.extract[org.bson.types.ObjectId](j)(format, Manifest.classType(classOf[org.bson.types.ObjectId])) should be("57b5b4a321e65efe0b7b5fd5")
    }

    "return same ObjectId if I don't have an implicit ObjectIdStringSerializer in scope" in {
      implicit val format = DefaultFormats
      val j = JString("57b5b4a321e65efe0b7b5fd5")
      j.extract[org.bson.types.ObjectId] should be("57b5b4a321e65efe0b7b5fd5")
    }

    "return same ObjectId if I do have an implicit ObjectIdStringSerializer in scope" in {
      implicit val format = DefaultFormats + new ObjectIdStringSerializer
      val j = JString("57b5b4a321e65efe0b7b5fd5")
      j.extract[org.bson.types.ObjectId] should be("57b5b4a321e65efe0b7b5fd5")
    }
  }
}