code:

    int nextIndex = 0;
    Func<LomarfType, int, int, Action> actionGenerator = (lomarf, index, delay) => async () =>
    {
        await queue.WaitAsync(lomarf);
        // WaitAsync should only return when it's our turn
        Assert.Equal(nextIndex, index);
        // simulate execution
        await Task.Delay(delay * 1000);
        // increment the index counter before dequeuing, which will signal the next waiter
        nextIndex++;
        queue.DequeueLomarf(lomarf);
    };
    
    var tasks = Enumerable.Range(0, delays.Length).Select(x => Task.Factory.StartNew(actionGenerator(lomarfs[x], x, delays[x]))).ToArray();
    
    // execute all tasks simultaneously
    Task.WaitAll(tasks);
    Assert.Equal(nextIndex, delays.Length);