Add "AnEmptyQueue.ThrowsWhenDequeue"
Add "AnEmptyQueue.DoesntThrowWhenEnqueue"
Refactor the test code

Add AnEmptyQueue fixture
Add "AQueueWithOneElement.HasSizeOne"
Add "AQueueWithOneElement.IsntEmpty"
Add "AnEmptyQueue.IsEmpty"
Refactor the test code

Add AQueueWithOneElement fixture
Add "AQueueWithOneElement.DoesntThrowWhenDequeue"
Add "AQueueWithOneElement.HasSizeZeroAfterDequeue"