t.Fatalf("have %v, want nil", err)
	}
	text := buff.String()

	if text != expected {
		t.Errorf("have %v, want %v", text, expected)
	}
}

func TestIssue5880(t *testing.T) {
	type T []byte
	data, err := Marshal(T{192, 168, 0, 1})
	if err != nil {
		t.Errorf("Marshal error: %v", err)
	}
	if !utf8.Valid(data) {