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: cpu_s390x_test.go
    path of file: ./repos/gccrs/libgo/go/internal/cpu
    
    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 cpu_test

import (
	"errors"
	. "internal/cpu"
	"os"
	"regexp"
	"testing"
)

func getFeatureList() ([]string, error) {
	cpuinfo, err := os.ReadFile("/proc/cpuinfo")
	if err != nil {
		return nil, err
	}
	r := regexp.MustCompile("features\\s*:\\s*(.*)")
	b := r.FindSubmatch(cpuinfo)
	if len(b) < 2 {
		return nil, errors.New("no feature list in /proc/cpuinfo")
	}
	return regexp.MustCompile("\\s+").Split(string(b[1]), -1), nil
}

func TestS390XAgainstCPUInfo(t *testing.T) {
	// mapping of linux feature strings to S390X fiel
    
func TestS390XAgainstCPUInfo(t *testing.T) {
	// mapping of linux feature strings to S390X fields
	mapping := make(map[string]*bool)
	for _, option := range Options {
		mapping[option.Name] = option.Feature
	}

	// these must be true on the machines Go supports
	mandatory := make(map[string]bool)
	mandatory["zarch"] = false
	mandatory["eimm"] = false
	mandatory["ldisp"] = false
	mandatory["stfle"] = false

	features, err := getFeatureList()
	if err != nil {
		t.Error(err)
	}
	for _, feature := range features {
		if _, ok := mandatory[feature]; ok {
			mandatory[feature] = true
		}
		if flag, ok := mapping[feature]; ok {
			if !*flag {
				t.Errorf("feature '%v' not detected", feature)
			}
		} else {
			t.Logf("no entry for '%v'", feature)
		}
	}
	for k, v := range mandatory {
		if !v {
			t.Errorf("mandatory feature '%v' not detected", k)
		}
	}
}