[Tests] assessment

[michellexliu]

Create a new file spec/controllers/assessment_controller_spec.rb and add the following tests:

Sprint 1

• [Functionality test] autograde_done
• [Functionality test] regrade
• [Functionality test] regrade batch
• [Functionality test] regrade all
• [Functionality test] bulk export

Sprint 2

• [Functionality test] bulkGrade
• [Functionality test] bulkGrade_complete
• [Functionality test] handin
• [Functionality test] local_submit
• [Functionality test] handout