It's a little different - we don't need to specify how to create a SparkContext in each test, so our version of `withSpark` does it automatically. Our version also sets Kryo as the serializer, which is useful to test.

If having two versions of LocalSparkContext is confusing, we could add this `withSpark` as an overload is Spark core and use a separate trait for setting Kryo. What do you think?