Scala: Write Random Values to JSON and Save in File then Analyze in Spark

I would like to write ten (or a billion) events to JSON and save as files.

I am writing in a Databricks notebook in Scala. I want the JSON string to have randomly generated values for fields like "Carbs":

{"Username": "patient1", "Carbs": 92, "Bolus": 24, "Basal": 1.33, "Date": 2017-06-28, "Timestamp": 2017-06-28 21:59:...}

I successfully used the following to write the date to an Array() and then save as a JSON file.

val dateDF = spark.range(10)
  .withColumn("today", current_date())

But what is the best way to write random values to an Array and then save the Array as a JSON file?