Add Course Controller Tests

[sophiacrennan]

Problem: We need to add Course Controller tests
Solution: Using the tests that are already made for Course Controller as an example, write more tests

Description: Since we now have a testing framework, it's time to write tests for all our controllers! You can use the testing documentation and the course controller tests as an example to write more Course Controller tests. The current tests for Course Controller don't test everything - it is just an example of how to write tests

Specs:

• write tests for each method in the Course Controller
• document any issues you had that others might encounter and document the solution

If blocked, contact @VKong6019