WIP: Add test to assert state of submission changes

When a user closes an exercise for a submission that needs input check that the
submissions state is changed to done.
>Go ahead and run bin/console and then paste in this query:
`UserExercise.where(6, 'ruby', 'word-count').first`
What happens?

I don't know why I wrote a `where` clause with a bunch of values, I made a basic mistake. The correct way of writing that query would be to supply the keys for each value.

`UserExercise.where(id: 6, language: 'ruby', slug: 'word-count').first`