@Test
    public void canRetrieveAColumnFromGrid() {

        for (int x = 0, size = sudoku.getGridLength(); x < size; x++)
            for (int y = 0; y < size; y++)
                sudoku.setCellValue(x, y, x);

        int[] column;
        for (int i = 0, size = sudoku.getGridLength(); i < size; i++) {
            column = sudoku.getGridColumn(i);
            assertThat(column.length).isEqualTo(sudoku.getGridLength());
            for (int j = 0; j < size; j++)
                assertThat(column[j]).isEqualTo(i);
        }
    }