public void SmallestNotExisting_NotInArray_WithOn_Returns5()
        {
            int[]        arr = new int[] { 1, 3, 6, 4, 1, 2 };
            ArrayService ars = new ArrayService();
            int          sm  = ars.SmallestNotIn(arr, true);

            Assert.Equal(5, sm);
        }
        public void SmallestNotExisting_NotInArray_WithOn_Returns1()
        {
            int[]        arr = new int[] { -1, -3 };
            ArrayService ars = new ArrayService();
            int          sm  = ars.SmallestNotIn(arr, true);

            Assert.Equal(1, sm);
        }
        public void SmallestNotExisting_NotInArray()
        {
            int[]        arr = new int[] { 1, 2, 3 };
            ArrayService ars = new ArrayService();
            int          sm  = ars.SmallestNotIn(arr);

            Assert.Equal(4, sm);
        }