Test Coverage Question

hostname.go

package main

import (
	"log"
	"os"
)

// METHOD1
// Typical Method
func GetHostname() string {
	name, err := os.Hostname()
	if err != nil {
		log.Fatalln("Could not get hostname", err)
	}
	if name == "" {
		log.Println("WARNING: Hostname is blank!")
	}
	return name
}

// METHOD2
type HostnameResolver interface {
	Name() (string, error)
}

type osHostnameResolver struct {
	resolver func() (string, error)
}

func (hr *osHostnameResolver) Name() (string, error) {
	return hr.resolver()
}

// Dependency Injected and Dependency Inverted
func GetHostnameDI(hr HostnameResolver) string {
	name, err := hr.Name()
	if err != nil {
		log.Println("Could not get hostname", err)
	}
	if name == "" {
		log.Println("WARNING: Hostname is blank!")
	}
	return name
}

hostname_test.go

package main

import (
	"errors"
	"os"
	"testing"
)

func TestGetHostname(t *testing.T) {
	_ = GetHostname()
}

func TestGetHostnameDIwithOS(t *testing.T) {
	_ = GetHostnameDI(&osHostnameResolver{os.Hostname})
}

func TestGetHostnameDIwithBlank(t *testing.T) {
	_ = GetHostnameDI(&osHostnameResolver{
		func() (string, error) {
			return "", nil
		},
	})
}

func TestGetHostnameDIwithError(t *testing.T) {
	_ = GetHostnameDI(&osHostnameResolver{
		func() (string, error) {
			return "", errors.New("Vasko doesn't want to give you the hostname")
		},
	})
}