how do i force unit test to do whole stage codegen

[Koert Kuipers]

i wrote my own expression with eval and doGenCode, but doGenCode never gets
called in tests.

also as a test i ran this in a unit test:
spark.range(10).select('id as 'asId).where('id === 4).explain
according to
https://jaceklaskowski.gitbooks.io/mastering-apache-spark/spark-sql-whole-stage-codegen.html
this is supposed to show:

== Physical Plan ==WholeStageCodegen
:  +- Project [id#0L AS asId#3L]
:     +- Filter (id#0L = 4)
:        +- Range 0, 1, 8, 10, [id#0L]

but it doesn't. instead it shows:

== Physical Plan ==
*Project [id#12L AS asId#15L]
+- *Filter (id#12L = 4)
   +- *Range (0, 10, step=1, splits=Some(4))

so i am again missing the WholeStageCodegen. any idea why?

i create spark session for unit tests simply as:
val session = SparkSession.builder
  .master("local[*]")
  .appName("test")
  .config("spark.sql.shuffle.partitions", 4)
  .getOrCreate()