JAVA 8

static Random rand = new Random();

public static class TestDataEmptyArray
{
    public static int[] get_array()
    {
        return new int[0];
    }

}

public static class TestDataUniqueValues
{
    static int[] arr;

    public static int[] get_array()
    {
        int bound = rand.nextInt(100) + 2;
        arr = new int[bound];
        Set<Integer> set = new HashSet<>();

        while (set.size() < bound)
        {
            set.add(rand.nextInt(100000));
        }

        arr = set.stream().mapToInt(Integer::intValue).toArray();

        return arr;
    }

    public static int get_expected_result()
    {
        int min_index = 0;

        for (int i = 1; i < arr.length; i++)
        {
            if (arr[i] < arr[min_index])
            {
                min_index = i;
            }
        }

        return min_index;
    }
}

public static class TestDataExactlyTwoDifferentMinimums
{
    static int[] arr;

    public static int[] get_array()
    {
        int bound = rand.nextInt(100) + 2;
        arr = new int[bound];
        Set<Integer> set = new HashSet<>();

        while (set.size() < bound - 1)
        {
            set.add(rand.nextInt(100000));
        }

        arr = set.stream().mapToInt(Integer::intValue).toArray();

        Arrays.sort(arr);
        arr[arr.length - 1] = arr[0];

        return arr;
    }

    public static int get_expected_result()
    {
        int min_index = 0;

        for (int i = 1; i < arr.length; i++)
        {
            if (arr[i] < arr[min_index])
            {
                min_index = i;
            }
        }

I wanted to go off track and use abstract classes, but everything ended up being more straightforward than I expected, haha.

        return min_index;
    }
}