@Test
         public void testNextSteps_normal_4direction() {
        int[][] ints = {
                {1, 2, 3},
                {4, PuzzuleNode.EMPTY, 6},
                {7, 8, 9}
        };

        List<Node> nextSteps = new PuzzuleNode(ints, 1, 1).nextSteps();

        assertThat(nextSteps.toString(),
                is("[[1, 2, 3][4, 8, 6][7, -1, 9], [1, -1, 3][4, 2, 6][7, 8, 9], [1, 2, 3][4, 6, -1][7, 8, 9], [1, 2, 3][-1, 4, 6][7, 8, 9]]"));
    }