package errors_test

import (
	"errors"
	"fmt"
	"os"
	"reflect"
	"testing"
)

func TestIs(t *testing.T) {
	err1 := errors.New("1")
	erra := wrapped{"wrap 2", err1}
	errb := wrapped{"wrap 3", erra}
...

if _, err := os.Open("non-existing"); err != nil {
	var pathError *os.PathError
	if errors.As(err, &pathError) {
		fmt.Println("Failed at path:", pathError.Path)
	} else {
		fmt.Println(err)
	}
}