pkg/util/exec: allow mocking of LookPath

pkg/kubelet/network/hairpin/hairpin.go

@@ -20,7 +20,6 @@ import (
 	"fmt"
 	"io/ioutil"
 	"net"
-	osexec "os/exec"
 	"path"
 	"regexp"
 	"strconv"
@@ -54,11 +53,11 @@ func setUpContainerInternal(e exec.Interface, containerPid int, containerInterfa
 }
 
 func findPairInterfaceOfContainerInterface(e exec.Interface, containerPid int, containerInterfaceName string) (string, error) {
-	nsenterPath, err := osexec.LookPath("nsenter")
+	nsenterPath, err := e.LookPath("nsenter")
 	if err != nil {
 		return "", err
 	}
-	ethtoolPath, err := osexec.LookPath("ethtool")
+	ethtoolPath, err := e.LookPath("ethtool")
 	if err != nil {
 		return "", err
 	}

pkg/kubelet/network/hairpin/hairpin_test.go

@@ -64,6 +64,9 @@ func TestFindPairInterfaceOfContainerInterface(t *testing.T) {
 					return exec.InitFakeCmd(&fcmd, cmd, args...)
 				},
 			},
+			LookPathFunc: func(file string) (string, error) {
+				return fmt.Sprintf("/fake-bin/%s", file), nil
+			},
 		}
 		name, err := findPairInterfaceOfContainerInterface(&fexec, 123, "eth0")
 		if test.expectErr {

pkg/util/exec/exec.go

@@ -27,6 +27,9 @@ type Interface interface {
 	// Command returns a Cmd instance which can be used to run a single command.
 	// This follows the pattern of package os/exec.
 	Command(cmd string, args ...string) Cmd
+
+	// LookPath wraps os/exec.LookPath
+	LookPath(file string) (string, error)
 }
 
 // Cmd is an interface that presents an API that is very similar to Cmd from os/exec.
@@ -62,6 +65,11 @@ func (executor *executor) Command(cmd string, args ...string) Cmd {
 	return (*cmdWrapper)(osexec.Command(cmd, args...))
 }
 
+// LookPath is part of the Interface interface
+func (executor *executor) LookPath(file string) (string, error) {
+	return osexec.LookPath(file)
+}
+
 // Wraps exec.Cmd so we can capture errors.
 type cmdWrapper osexec.Cmd
 

pkg/util/exec/exec_test.go

@@ -17,6 +17,7 @@ limitations under the License.
 package exec
 
 import (
+	osexec "os/exec"
 	"testing"
 )
 
@@ -81,3 +82,13 @@ func TestExecutorWithArgs(t *testing.T) {
 		t.Errorf("unexpected output: %q", string(out))
 	}
 }
+
+func TestLookPath(t *testing.T) {
+	ex := New()
+
+	shExpected, _ := osexec.LookPath("sh")
+	sh, _ := ex.LookPath("sh")
+	if sh != shExpected {
+		t.Errorf("unexpected result for LookPath: got %s, expected %s", sh, shExpected)
+	}
+}

pkg/util/exec/fake_exec.go

@@ -24,6 +24,7 @@ import (
 type FakeExec struct {
 	CommandScript []FakeCommandAction
 	CommandCalls  int
+	LookPathFunc  func(string) (string, error)
 }
 
 type FakeCommandAction func(cmd string, args ...string) Cmd
@@ -37,6 +38,10 @@ func (fake *FakeExec) Command(cmd string, args ...string) Cmd {
 	return fake.CommandScript[i](cmd, args...)
 }
 
+func (fake *FakeExec) LookPath(file string) (string, error) {
+	return fake.LookPathFunc(file)
+}
+
 // A simple scripted Cmd type.
 type FakeCmd struct {
 	Argv                 []string