Test should run and pass even when run on an environment that does not have Powershel.

builder/hyperv/iso/builder.go

@@ -7,6 +7,11 @@ package iso
 import (
 	"errors"
 	"fmt"
+	"log"
+	"os"
+	"strings"
+	"time"
+
 	"github.com/mitchellh/multistep"
 	hypervcommon "github.com/mitchellh/packer/builder/hyperv/common"
 	"github.com/mitchellh/packer/common"
@@ -16,10 +21,6 @@ import (
 	powershell "github.com/mitchellh/packer/powershell"
 	"github.com/mitchellh/packer/powershell/hyperv"
 	"github.com/mitchellh/packer/template/interpolate"
-	"log"
-	"os"
-	"strings"
-	"time"
 )
 
 const (
@@ -148,13 +149,7 @@ func (b *Builder) Prepare(raws ...interface{}) ([]string, error) {
 	log.Println(fmt.Sprintf("%s: %v", "VMName", b.config.VMName))
 
 	if b.config.SwitchName == "" {
-		// no switch name, try to get one attached to a online network adapter
-		onlineSwitchName, err := hyperv.GetExternalOnlineVirtualSwitch()
-		if onlineSwitchName == "" || err != nil {
-			b.config.SwitchName = fmt.Sprintf("packer-%s", b.config.PackerBuildName)
-		} else {
-			b.config.SwitchName = onlineSwitchName
-		}
+		b.config.SwitchName = b.detectSwitchName()
 	}
 
 	if b.config.Cpu < 1 {
@@ -455,11 +450,29 @@ func (b *Builder) checkRamSize() error {
 }
 
 func (b *Builder) checkHostAvailableMemory() string {
-	freeMB := powershell.GetHostAvailableMemory()
+	powershellAvailable, _, _ := powershell.IsPowershellAvailable()
 
-	if (freeMB - float64(b.config.RamSizeMB)) < LowRam {
-		return fmt.Sprintf("Hyper-V might fail to create a VM if there is not enough free memory in the system.")
+	if powershellAvailable {
+		freeMB := powershell.GetHostAvailableMemory()
+
+		if (freeMB - float64(b.config.RamSizeMB)) < LowRam {
+			return fmt.Sprintf("Hyper-V might fail to create a VM if there is not enough free memory in the system.")
+		}
 	}
 
 	return ""
 }
+
+func (b *Builder) detectSwitchName() string {
+	powershellAvailable, _, _ := powershell.IsPowershellAvailable()
+
+	if powershellAvailable {
+		// no switch name, try to get one attached to a online network adapter
+		onlineSwitchName, err := hyperv.GetExternalOnlineVirtualSwitch()
+		if onlineSwitchName != "" && err == nil {
+			return onlineSwitchName
+		}
+	}
+
+	return fmt.Sprintf("packer-%s", b.config.PackerBuildName)
+}

builder/hyperv/iso/builder_test.go

@@ -1,9 +1,10 @@
 package iso
 
 import (
-	"github.com/mitchellh/packer/packer"
 	"reflect"
 	"testing"
+
+	"github.com/mitchellh/packer/packer"
 )
 
 func testConfig() map[string]interface{} {
@@ -31,6 +32,7 @@ func TestBuilder_ImplementsBuilder(t *testing.T) {
 func TestBuilderPrepare_Defaults(t *testing.T) {
 	var b Builder
 	config := testConfig()
+
 	warns, err := b.Prepare(config)
 	if len(warns) > 0 {
 		t.Fatalf("bad: %#v", warns)

powershell/powershell.go

@@ -5,20 +5,20 @@
 package powershell
 
 import (
+	"bytes"
 	"fmt"
-	"log"
 	"io"
+	"io/ioutil"
+	"log"
 	"os"
 	"os/exec"
-	"strings"
-	"bytes"
-	"io/ioutil"
 	"strconv"
+	"strings"
 )
 
 const (
 	powerShellFalse = "False"
-	powerShellTrue = "True"
+	powerShellTrue  = "True"
 )
 
 type PowerShellCmd struct {
@@ -31,14 +31,14 @@ func (ps *PowerShellCmd) Run(fileContents string, params ...string) error {
 	return err
 }
 
-// Output runs the PowerShell command and returns its standard output. 
+// Output runs the PowerShell command and returns its standard output.
 func (ps *PowerShellCmd) Output(fileContents string, params ...string) (string, error) {
-	path, err := ps.getPowerShellPath();
+	path, err := ps.getPowerShellPath()
 	if err != nil {
-		return "", nil
+		return "", err
 	}
 
-	filename, err := saveScript(fileContents);
+	filename, err := saveScript(fileContents)
 	if err != nil {
 		return "", err
 	}
@@ -49,7 +49,7 @@ func (ps *PowerShellCmd) Output(fileContents string, params ...string) (string,
 	if !debug {
 		defer os.Remove(filename)
 	}
-	
+
 	args := createArgs(filename, params...)
 
 	if verbose {
@@ -93,13 +93,23 @@ func (ps *PowerShellCmd) Output(fileContents string, params ...string) (string,
 		log.Printf("stderr: %s", stderrString)
 	}
 
-	return stdoutString, err;	
+	return stdoutString, err
+}
+
+func IsPowershellAvailable() (bool, string, error) {
+	path, err := exec.LookPath("powershell")
+	if err != nil {
+		return false, "", err
+	} else {
+		return false, path, err
+	}
 }
 
 func (ps *PowerShellCmd) getPowerShellPath() (string, error) {
-	path, err := exec.LookPath("powershell")
-	if err != nil {
-		log.Fatal("Cannot find PowerShell in the path", err)
+	powershellAvailable, path, err := IsPowershellAvailable()
+
+	if !powershellAvailable {
+		log.Fatal("Cannot find PowerShell in the path")
 		return "", err
 	}
 
@@ -111,7 +121,7 @@ func saveScript(fileContents string) (string, error) {
 	if err != nil {
 		return "", err
 	}
-	
+
 	_, err = file.Write([]byte(fileContents))
 	if err != nil {
 		return "", err
@@ -132,7 +142,7 @@ func saveScript(fileContents string) (string, error) {
 }
 
 func createArgs(filename string, params ...string) []string {
-	args := make([]string,len(params)+4)
+	args := make([]string, len(params)+4)
 	args[0] = "-ExecutionPolicy"
 	args[1] = "Bypass"
 
@@ -141,9 +151,9 @@ func createArgs(filename string, params ...string) []string {
 
 	for key, value := range params {
 		args[key+4] = value
-	}	
+	}
 
-	return args;
+	return args
 }
 
 func GetHostAvailableMemory() float64 {
@@ -158,7 +168,6 @@ func GetHostAvailableMemory() float64 {
 	return freeMB
 }
 
-
 func GetHostName(ip string) (string, error) {
 
 	var script = `
@@ -174,7 +183,7 @@ try {
 
 	//
 	var ps PowerShellCmd
-	cmdOut, err := ps.Output(script, ip);
+	cmdOut, err := ps.Output(script, ip)
 	if err != nil {
 		return "", err
 	}
@@ -190,8 +199,8 @@ $administratorRole = [System.Security.Principal.WindowsBuiltInRole]::Administrat
 return $principal.IsInRole($administratorRole)
 `
 
-    var ps PowerShellCmd
-	cmdOut, err := ps.Output(script);
+	var ps PowerShellCmd
+	cmdOut, err := ps.Output(script)
 	if err != nil {
 		return false, err
 	}
@@ -200,14 +209,13 @@ return $principal.IsInRole($administratorRole)
 	return res == powerShellTrue, nil
 }
 
-
 func ModuleExists(moduleName string) (bool, error) {
 
 	var script = `
 param([string]$moduleName)
 (Get-Module -Name $moduleName) -ne $null
 `
-    var ps PowerShellCmd
+	var ps PowerShellCmd
 	cmdOut, err := ps.Output(script)
 	if err != nil {
 		return false, err
@@ -215,7 +223,7 @@ param([string]$moduleName)
 
 	res := strings.TrimSpace(string(cmdOut))
 
-	if(res == powerShellFalse){
+	if res == powerShellFalse {
 		err := fmt.Errorf("PowerShell %s module is not loaded. Make sure %s feature is on.", moduleName, moduleName)
 		return false, err
 	}
@@ -249,7 +257,7 @@ $productKeyNode.InnerText = $productKey
 $unattend.Save($path)
 `
 
-  var ps PowerShellCmd
-  err := ps.Run(script, path, productKey)
-  return err
+	var ps PowerShellCmd
+	err := ps.Run(script, path, productKey)
+	return err
 }

powershell/powershell_test.go

@@ -6,11 +6,13 @@ import (
 )
 
 func TestOutput(t *testing.T) {
+
 	var ps PowerShellCmd
 
-	powerShellPath, err := ps.getPowerShellPath()
-	if err != nil {
-		t.Skipf("powershell not installed: %s", err)
+	powershellAvailable, _, _ := IsPowershellAvailable()
+
+	if !powershellAvailable {
+		t.Skipf("powershell not installed")
 		return
 	}
 
@@ -43,17 +45,18 @@ func TestOutput(t *testing.T) {
 }
 
 func TestRunFile(t *testing.T) {
+	var ps PowerShellCmd
+
+	powershellAvailable, _, _ := IsPowershellAvailable()
+
+	if !powershellAvailable {
+		t.Skipf("powershell not installed")
+		return
+	}
+
 	var blockBuffer bytes.Buffer
 	blockBuffer.WriteString(`param([string]$a, [string]$b, [int]$x, [int]$y) if (Test-Path variable:global:ProgressPreference){$ProgressPreference="SilentlyContinue"}; $n = $x + $y; Write-Output "$a $b $n";`)
 
-	var ps PowerShellCmd
-	
-	powerShellPath, err := ps.getPowerShellPath()
-	if err != nil {
-		t.Skipf("powershell not installed: %s", err)
-		return
-	}
-	
 	cmdOut, err := ps.Output(blockBuffer.String(), "a", "b", "5", "10")
 
 	if err != nil {