nsenter: add tests

Signed-off-by: Andrey Vagin <avagin@openvz.org>

namespaces/nsenter/nsenter_test.go

@@ -0,0 +1,99 @@
+package nsenter
+
+import (
+	"encoding/json"
+	"fmt"
+	"os"
+	"os/exec"
+	"os/signal"
+	"strings"
+	"syscall"
+	"testing"
+)
+
+type pid struct {
+	Pid int `json:"Pid"`
+}
+
+func TestNsenterAlivePid(t *testing.T) {
+	args := []string{"nsenter-exec"}
+	r, w, err := os.Pipe()
+	if err != nil {
+		t.Fatalf("failed to create pipe %v", err)
+	}
+
+	cmd := &exec.Cmd{
+		Path:       os.Args[0],
+		Args:       args,
+		ExtraFiles: []*os.File{w},
+		Env:        []string{fmt.Sprintf("_LIBCONTAINER_INITPID=%d", os.Getpid())},
+	}
+
+	if err := cmd.Start(); err != nil {
+		t.Fatalf("nsenter failed to start %v", err)
+	}
+	w.Close()
+
+	decoder := json.NewDecoder(r)
+	var pid *pid
+
+	if err := decoder.Decode(&pid); err != nil {
+		t.Fatalf("%v", err)
+	}
+
+	if err := cmd.Wait(); err != nil {
+		t.Fatalf("nsenter exits with a non-zero exit status")
+	}
+	p, err := os.FindProcess(pid.Pid)
+	if err != nil {
+		t.Fatalf("%v", err)
+	}
+	p.Wait()
+}
+
+func TestNsenterInvalidPid(t *testing.T) {
+	args := []string{"nsenter-exec"}
+
+	cmd := &exec.Cmd{
+		Path: os.Args[0],
+		Args: args,
+		Env:  []string{"_LIBCONTAINER_INITPID=-1"},
+	}
+
+	err := cmd.Run()
+	if err == nil {
+		t.Fatal("nsenter exits with a zero exit status")
+	}
+}
+
+func TestNsenterDeadPid(t *testing.T) {
+
+	c := make(chan os.Signal)
+	signal.Notify(c, syscall.SIGCHLD)
+	dead_cmd := exec.Command("true")
+	if err := dead_cmd.Start(); err != nil {
+		t.Fatal(err)
+	}
+	defer dead_cmd.Wait()
+	<-c // dead_cmd is zombie
+
+	args := []string{"nsenter-exec"}
+
+	cmd := &exec.Cmd{
+		Path: os.Args[0],
+		Args: args,
+		Env:  []string{fmt.Sprintf("_LIBCONTAINER_INITPID=%d", dead_cmd.Process.Pid)},
+	}
+
+	err := cmd.Run()
+	if err == nil {
+		t.Fatal("nsenter exits with a zero exit status")
+	}
+}
+
+func init() {
+	if strings.HasPrefix(os.Args[0], "nsenter-") {
+		os.Exit(0)
+	}
+	return
+}