Scala Jackson json deserializer for Microsoft json date format to joda DateTime

MicrosoftJsonDateDeserializer.scala

import com.fasterxml.jackson.databind.{DeserializationContext, JsonDeserializer}
import org.joda.time.{DateTimeZone, DateTime}
import com.fasterxml.jackson.core.JsonParser
import java.io.IOException

class MicrosoftJsonDateDeserializer extends JsonDeserializer[DateTime] {
  val Pattern = """\/Date\((\d+)([-+]\d+)?\)\/""".r

  def deserialize(jsonParser: JsonParser, deserializationContext: DeserializationContext): DateTime = {
    val dateString = jsonParser.getText

    dateString match {
      case Pattern(millis, null) => new DateTime(millis.toLong, DateTimeZone.forOffsetHours(0))
      case Pattern(millis, tz) => new DateTime(millis.toLong, DateTimeZone.forID(tz))
      case null => null
      case _ => throw new IOException(s"wrong date time format: $dateString")
    }
  }
}

MicrosoftJsonDateDeserializerTest.scala

import org.specs2.mutable._
import org.specs2.mock.Mockito

import com.fasterxml.jackson.databind.DeserializationContext
import com.fasterxml.jackson.core._
import org.joda.time.{DateTimeZone, DateTime}
import java.io.IOException

class MicrosoftJsonDateDeserializerTest extends Specification with Mockito{

  "deserializing Some(/Date(1357232623030+0500)/)" should {
    "return the correct date" in {
      val deserializer = new MicrosoftJsonDateDeserializer
      val parser = mock[JsonParser]
      parser.getText returns "/Date(1357232623030+0500)/"
      val ctx = mock[DeserializationContext]
      val result = deserializer.deserialize(parser, ctx)
      result should beEqualTo(new DateTime(1357232623030L, DateTimeZone.forOffsetHours(5)))
    }
  }

  "deserializing Some(/Date(1357232623030)/)" should {
    "return the correct date" in {
      val deserializer = new MicrosoftJsonDateDeserializer
      val parser = mock[JsonParser]
      parser.getText returns "/Date(1357232623030)/"
      val ctx = mock[DeserializationContext]
      val result = deserializer.deserialize(parser, ctx)
      result should beEqualTo(new DateTime(1357232623030L, DateTimeZone.forOffsetHours(0)))
    }
  }

  "deserializing null" should {
    "return null" in {
      val deserializer = new MicrosoftJsonDateDeserializer
      val parser = mock[JsonParser]
      val ctx = mock[DeserializationContext]
      val result = deserializer.deserialize(parser, ctx)
      result should beNull
    }
  }

  "deserializing 'invaliddate'" should {
    "throw an exception" in {
      val deserializer = new MicrosoftJsonDateDeserializer
      val parser = mock[JsonParser]
      parser.getText returns "invaliddate"
      val ctx = mock[DeserializationContext]

      deserializer.deserialize(parser, ctx) must throwA[IOException]
    }
  }
}