…e previous version didn't match with the `composer.json` one.

…ts.0". Expected scalar, but got object."

…n: The service "jms_serializer.stopwatch_subscriber" has a dependency on a non-existent service "debug.stopwatch"". More info: schmittjoh/JMSSerializerBundle#624

…imilarComparator#assertEquals` not being compatible with `SebastianBergmann\Comparator\ObjectComparator#assertEquals`

…t` over `null`s: "count(): Parameter must be an array or an object that implements Countable"

* Make the `UnitTestCase` class extend from `MockeryTestCase` in order to close and check Mockery assertions. This is the recommended way since Mockery 1.0: http://docs.mockery.io/en/latest/reference/phpunit_integration.html

Move `CourseIdStub` to test namespace