mock input dstream apache spark

I am trying to mock the input dstream while writing a spark stream unit test. I am able to mock the RDD but when I am trying to convert them into dstream, dstream object is coming up empty. I have used the following code-

val lines = mutable.Queue[RDD[String]]()
val dstream = streamingContext.queueStream(lines)

// append data to DStream
lines += sparkContext.makeRDD(Seq("To be or not to be.", "That is the question."))

Any help regarding the same will be highly appreciated.