Test the classifier reducers (#4900)
Test the classifier reducers (#4900)

* Add tests for updating the subject queue
Test appending and prepending subjects to the upcoming queue.

* Add tests for next subject

* Test reset subjects

* Test create classification

* Test resume classification

* Test set workflow

* Test classification for empty subject queue
Check that the classification is cleared for an empty subject queue, on next subject.

amyrebecca/Panoptes-Front-End,amyrebecca/Panoptes-Front-End,zooniverse/Panoptes-Front-End,amyrebecca/Panoptes-Front-End