func TestLookupUserPopulatesAllFields(t *testing.T) {
	u, err := findUsername("allfields", strings.NewReader(testUserFile))
	if err != nil {
		t.Fatal(err)
	}
	want := &User{
		Username: "allfields",
		Uid:      "6",
		Gid:      "12",
		Name:     "mansplit",
		HomeDir:  "/home/allfields",
	}
	if !reflect.DeepEqual(u, want) {
		t.Errorf("findUsername: got %#v, want %#v", u, want)
	}
}

	}
	if v, err := readColonFile(r, matchUserIndexValue(uid, 2), 6); err != nil {
		return nil, err
	} else if v != nil {
		return v.(*User), nil
	}
	return nil, UnknownUserIdError(i)
}

func findUsername(name string, r io.Reader) (*User, error) {
	if v, err := readColonFile(r, matchUserIndexValue(name, 0), 6); err != nil {
		return nil, err
	} else if v != nil {
		return v.(*User), nil
	}