public async Task enqueue_should_put_item_on_queue()
        {
            var sut = new MemoryQueue<object>();
            var expected = new object();

            await sut.EnqueueAsync(expected);
            var actual = await sut.DequeueAsync();

            actual.Should().BeSameAs(expected);
        }
        public async Task dequeue_item_should_work()
        {
            var sut      = new MemoryQueue <object>();
            var expected = new object();
            await sut.EnqueueAsync(expected);

            var actual = await sut.DequeueAsync();

            actual.Should().BeSameAs(expected);
        }