return fmt.Sprintf("string=%d", s.v)
}

type errorer struct {
	v int
}

func (s *errorer) Error() string {
	return fmt.Sprintf("error=%d", s.v)
}

func TestStringer(t *testing.T) {
	s := &myStringer{3}
	b := new(strings.Builder)
	tmpl := Must(New("x").Parse("{{.}}"))
	if err := tmpl.Execute(b, s); err != nil {
		t.Fatal(err)
	}
	var expect = "string=3"