The smallest possible implementation of a queue. Need simplicity? Here it is. 100% code coverage in tests, all alternatives I could think of are taken into consideration as well. Hence, it is as robust as it can be... (that statement may backfire, be gentle 😅)
The specification is the following:
All methods do exactly what they are meant to do in the provided implementation (QueueImpl). You may reimplement this interface, extend it, do as you wish, really.