code: @Test public void shouldDetectChangeForUpdatedGroupsOnly(){
    victim.updateHashForGroup("hash1",GROUP1_NAME);
    victim.updateHashForGroup("hash1",GROUP2_NAME);
    victim.reset();
    assertTrue(victim.isChanged(GROUP1_NAME));
    assertTrue(victim.isChanged(GROUP2_NAME));
    victim.updateHashForGroup("hash1",GROUP1_NAME);
    victim.updateHashForGroup("hash1",GROUP2_NAME);
    assertFalse(victim.isChanged(GROUP1_NAME));
    assertFalse(victim.isChanged(GROUP2_NAME));
    assertTrue(victim.isChanged(GROUP3_NAME));
  }
  