src/errors/errors_test.go

// Copyright 2011 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package errors_test

import (
	"errors"
	"fmt"
	"testing"
)

func TestNewEqual(t *testing.T) {
	// Different allocations should not be equal.
	if errors.New("abc") == errors.New("abc") {
		t.Errorf(`New("abc") == New("abc")`)
	}
	if errors.New("abc") == errors.New("xyz") {
		t.Errorf(`New("abc") == New("xyz")`)
	}

	// Same allocation should be equal to itself (not crash).
	err := errors.New("jkl")
	if err != err {
		t.Errorf(`err != err`)
	}
}

func TestErrorMethod(t *testing.T) {
	err := errors.New("abc")
	if err.Error() != "abc" {
		t.Errorf(`New("abc").Error() = %q, want %q`, err.Error(), "abc")
	}
}

func ExampleNew() {
	err := errors.New("emit macho dwarf: elf header corrupted")
	if err != nil {
		fmt.Print(err)
	}
	// Output: emit macho dwarf: elf header corrupted
}

// The fmt package's Errorf function lets us use the package's formatting
// features to create descriptive error messages.
func ExampleNew_errorf() {
	const name, id = "bimmler", 17
	err := fmt.Errorf("user %q (id %d) not found", name, id)
	if err != nil {
		fmt.Print(err)
	}
	// Output: user "bimmler" (id 17) not found
}

func ExampleJoin() {
	err1 := errors.New("err1")
	err2 := errors.New("err2")
	err := errors.Join(err1, err2)
	fmt.Println(err)
	if errors.Is(err, err1) {
		fmt.Println("err is err1")
	}
	if errors.Is(err, err2) {
		fmt.Println("err is err2")
	}
	// Output:
	// err1
	// err2
	// err is err1
	// err is err2
}