{in: "", user: "no-such-user", gid: "2345", gids: []string{"2345"}},
	// Error cases.
	{in: "", user: "", gid: "2345", err: true},
	{in: "", user: "joanna", gid: "bad", err: true},
}

func TestListGroups(t *testing.T) {
	for _, tc := range listGroupsTests {
		u := &User{Username: tc.user, Gid: tc.gid}
		got, err := listGroupsFromReader(u, strings.NewReader(tc.in))
		if tc.err {
			if err == nil {