@Test
    public void testNextSteps_normal_3direction() {
        int[][] ints = {
                {1, 2, 3},
                {4, 6, PuzzuleNode.EMPTY},
                {7, 8, 9}
        };

        List<Node> nextSteps = new PuzzuleNode(ints, 1, 2).nextSteps();

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