Improve findOneBySlug using DQL
Adds fixture for creating media
Adds simple tests for MediaController
Use getOneOrNullResult
Adds test to check a 404 is thrown if a non-existant slug is passed to MediaRepository
Tests for /media/{id}speakers' route
Throw 404 if MediaController::speakersAction is passed invalid id
Fix Get Speaker throwing a 500 if requesting a non-existant speaker
Throw 404 if media is not found in MediaController::rateAction
Adds 3 tests for setting a media item's rating