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

        List<Node> nextSteps = new PuzzuleNode(ints, 2, 2).nextSteps();

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