RandomFromFixedSequence example

RandomFromFixedSequence.cs

public class RandomFromFixedSequence<T> : ICustomization
{
    private IEnumerator<int> randomizer;
    private List<T> sequence;

    public void Customize(IFixture fixture)
    {
        this.sequence = fixture.CreateMany<T>().ToList();
        this.randomizer = new RoundRobinSequence(0, sequence.Count - 1).GetEnumerator();
        fixture.Register(PickRandomItemFromSequence);
    }

    private T PickRandomItemFromSequence()
    {
        this.randomizer.MoveNext();
        var randomIndex = this.randomizer.Current;
        return sequence[randomIndex];
    }
}

RoundRobinSequence.cs

public class RoundRobinSequence : IEnumerable<int>
{
    private readonly int min;
    private readonly int max;
    private int current;

    public RoundRobinSequence(int min, int max)
    {
        this.min = min;
        this.max = max;
        this.current = min;
    }

    public IEnumerator<int> GetEnumerator()
    {
        while (true)
        {
            current++;
            if (current > max)
            {
                current = current % 2 == 0 ? min + 1 : min;
            }
            yield return current;
            current++;
        }
    }

    IEnumerator IEnumerable.GetEnumerator() => this.GetEnumerator();
}