Recent development work identified a number of minor enhancements to the "sub-operator" unit tests:
- Create a SubOperatorTest base class to do routine setup and shutdown.
- Additional methods to simplify creating complex schemas with field widths.
- Define a test workspace with plugin-specific options (as for the CSV storage plugin)
- When verifying row sets, add methods to verify and release just the "actual" batch in addition to the existing method for verify and free both the actual and expected batches.