You are an expert in writing code in many different languages. Your goal is to perform code completion for the following code, keeping in mind the rest of the code and the file meta data.
    Metadata details:
    filename: errors_test.go
    path of file: ./repos/gccrs/libgo/go/fmt
    
    the code of the file until where you have to start completion: // Copyright 2018 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 fmt_test

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

func TestErrorf(t *testing.T) {
	// n
    
func TestErrorf(t *testing.T) {
	// noVetErrorf is an alias for fmt.Errorf that does not trigger vet warnings for
	// %w format strings.
	noVetErrorf := fmt.Errorf

	wrapped := errors.New("inner error")
	for _, test := range []struct {
		err        error
		wantText   string
		wantUnwrap error
	}{{
		err:        fmt.Errorf("%w", wrapped),
		wantText:   "inner error",
		wantUnwrap: wrapped,
	}, {
		err:        fmt.Errorf("added context: %w", wrapped),
		wantText:   "added context: inner error",
		wantUnwrap: wrapped,
	}, {
		err:        fmt.Errorf("%w with added context", wrapped),
		wantText:   "inner error with added context",
		wantUnwrap: wrapped,
	}, {
		err:        fmt.Errorf("%s %w %v", "prefix", wrapped, "suffix"),
		wantText:   "prefix inner error suffix",
		wantUnwrap: wrapped,
	}, {
		err:        fmt.Errorf("%[2]s: %[1]w", wrapped, "positional verb"),
		wantText:   "positional verb: inner error",
		wantUnwrap: wrapped,
	}, {
		err:      fmt.Errorf("%v", wrapped),
		wantText: "inner error",
	}, {
		err:      fmt.Errorf("added context: %v", wrapped),
		wantText: "added context: inner error",
	}, {
		err:      fmt.Errorf("%v with added context", wrapped),
		wantText: "inner error with added context",
	}, {
		err:      noVetErrorf("%w is not an error", "not-an-error"),
		wantText: "%!w(string=not-an-error) is not an error",
	}, {
		err:      noVetErrorf("wrapped two errors: %w %w", errString("1"), errString("2")),
		wantText: "wrapped two errors: 1 %!w(fmt_test.errString=2)",
	}, {
		err:      noVetErrorf("wrapped three errors: %w %w %w", errString("1"), errString("2"), errString("3")),
		wantText: "wrapped three errors: 1 %!w(fmt_test.errString=2) %!w(fmt_test.errString=3)",
	}, {
		err:        fmt.Errorf("%w", nil),
		wantText:   "%!w(<nil>)",
		wantUnwrap: nil, // still nil
	}} {
		if got, want := errors.Unwrap(test.err), test.wantUnwrap; got != want {
			t.Errorf("Formatted error: %v\nerrors.Unwrap() = %v, want %v", test.err, got, want)
		}
		if got, want := test.err.Error(), test.wantText; got != want {
			t.Errorf("err.Error() = %q, want %q", got, want)
		}
	}
}