t.Errorf("findGroupName(%s): got unexpected error %v", tt.name, terr)
			}
		} else {
			if err != nil {
				t.Fatalf("findGroupName(%s): got unexpected error %v", tt.name, err)
			}
			if got.Gid != tt.gid {
				t.Errorf("findGroupName(%s): got gid %v, want %s", tt.name, got.Gid, tt.gid)
			}
			if got.Name != tt.name {
				t.Errorf("findGroupName(%s): got name %s, want %s", tt.name, got.Name, tt.name)
			}
		}
	}
}

	if v, err := readColonFile(r, matchGroupIndexValue(id, 2), 3); err != nil {
		return nil, err
	} else if v != nil {
		return v.(*Group), nil
	}
	return nil, UnknownGroupIdError(id)
}

func findGroupName(name string, r io.Reader) (*Group, error) {
	if v, err := readColonFile(r, matchGroupIndexValue(name, 0), 3); err != nil {
		return nil, err
	} else if v != nil {
		return v.(*Group), nil
	}