done for method isGroupGood of GroupIndex
using assertTrue and assertFalse in junit proerply
public class GroupIndexTest {

    /**
     * Test of toPrint method, of class GroupIndex.
     */
    @Test
    public void testToPrint() {
        System.out.println("toPrint");
        Sudoku s = new Sudoku();
        s.setMemberByRow(1, 1, 2, 3, 4, 5, 6, 7, 8, 9);
        s.setMemberByRow(2, 1, 2, 3, 0, 5, 6, 1, 8, 0);
        s.toPrint();
        GroupIndex instance = new GroupIndex(s);
        assertTrue(instance.isGroupGood(1));
        assertFalse(instance.isGroupGood(2));
    }
}