Ticket Get Comments Issues

I am tried to work on get comment ticket but all the tests are not passed yet. I have spend a lot time on that but not managed to solve the issue.

When I run the test it shows me the following:

“com.mongodb.MongoCommandException: Command failed with error 40323 (Location40323): ‘A pipeline stage specification object must contain exactly one field.’”
Any thought?

Please read other threads with similar title or same error as yours. Good chances you will find the information you are looking for.