Get all transitions

When you create test cases you normally want to check all transitions between states or values. So how do you get a list of values to cover all transitions?

Well I started to Google, could not find any good example, probably because I didn’t use the correct word.

Then I asked Gemini and got some code, that didn’t work. And then some updated code, that didn’t work, and then….

Back to paper and pen and found a quite simple soulution.

public static int[] GenerateAllTransitionSeries(int[] numbers)
{
    if (numbers.Length < 2) throw new ArgumentException("Invalid array size, must be at least 2", nameof(numbers));

    int size = numbers.Length;

    List<int> series = new List<int>();

    int top = size - 1;
    int back = top - 1;

    for (int i = 0; i < size; i++)
    {
        series.Add(numbers[i]);
    }
    series.Add(numbers[back]);
    if (back > 0)
    {
        back--;
        series.Add(numbers[back]);
        int index = top;
        while (true)
        {
            series.Add(numbers[index]);
            if (index == top)
            {
                series.Add(numbers[back]);
                if (back == 0)
                {
                    break;
                }
                back--;
                index = back + 1;
            }
            index++;
            series.Add(numbers[back]);
        }
    }

    return series.ToArray();
}