libcontainer/configs: improve CommandHook unit tests

Test that CommandHook actually executes a new process with the given env
variables, parameters and json state.

This commit also solves an issue with the previous approach that was calling
'os.Exit(0)' failing to signal test failures.

Signed-off-by: Mauricio Vásquez <mauricio@kinvolk.io>

libcontainer/configs/config_test.go

@@ -3,6 +3,7 @@ package configs_test
 import (
 	"encoding/json"
 	"fmt"
+	"io/ioutil"
 	"os"
 	"reflect"
 	"testing"
@@ -160,18 +161,45 @@ func TestCommandHookRun(t *testing.T) {
 		Pid:     1,
 		Bundle:  "/bundle",
 	}
-	timeout := time.Second
+
+	stateJson, err := json.Marshal(state)
+	if err != nil {
+		t.Fatal(err)
+	}
+
+	verifyCommandTemplate := `#!/bin/sh
+if [ "$1" != "testarg" ]; then
+	echo "Bad value for $1. Expected 'testarg', found '$1'"
+	exit 1
+fi
+if [ -z "$FOO" ] || [ "$FOO" != BAR ]; then
+	echo "Bad value for FOO. Expected 'BAR', found '$FOO'"
+	exit 1
+fi
+expectedJson=%q
+read JSON
+if [ "$JSON" != "$expectedJson" ]; then
+	echo "Bad JSON received. Expected '$expectedJson', found '$JSON'"
+	exit 1
+fi
+exit 0
+	`
+	verifyCommand := fmt.Sprintf(verifyCommandTemplate, stateJson)
+	filename := "/tmp/runc-hooktest.sh"
+	os.Remove(filename)
+	if err := ioutil.WriteFile(filename, []byte(verifyCommand), 0700); err != nil {
+		t.Fatalf("Failed to create tmp file: %v", err)
+	}
+	defer os.Remove(filename)
 
 	cmdHook := configs.NewCommandHook(configs.Command{
-		Path:    os.Args[0],
-		Args:    []string{os.Args[0], "-test.run=TestHelperProcess"},
-		Env:     []string{"FOO=BAR"},
-		Dir:     "/",
-		Timeout: &timeout,
+		Path: filename,
+		Args: []string{filename, "testarg"},
+		Env:  []string{"FOO=BAR"},
+		Dir:  "/",
 	})
 
-	err := cmdHook.Run(state)
-	if err != nil {
+	if err := cmdHook.Run(state); err != nil {
 		t.Errorf(fmt.Sprintf("Expected error to not occur but it was %+v", err))
 	}
 }
@@ -184,26 +212,15 @@ func TestCommandHookRunTimeout(t *testing.T) {
 		Pid:     1,
 		Bundle:  "/bundle",
 	}
-	timeout := (10 * time.Millisecond)
+	timeout := 100 * time.Millisecond
 
 	cmdHook := configs.NewCommandHook(configs.Command{
-		Path:    os.Args[0],
-		Args:    []string{os.Args[0], "-test.run=TestHelperProcessWithTimeout"},
-		Env:     []string{"FOO=BAR"},
-		Dir:     "/",
+		Path:    "/bin/sleep",
+		Args:    []string{"/bin/sleep", "1"},
 		Timeout: &timeout,
 	})
 
-	err := cmdHook.Run(state)
-	if err == nil {
+	if err := cmdHook.Run(state); err == nil {
 		t.Error("Expected error to occur but it was nil")
 	}
 }
-
-func TestHelperProcess(*testing.T) {
-	fmt.Println("Helper Process")
-	os.Exit(0)
-}
-func TestHelperProcessWithTimeout(*testing.T) {
-	time.Sleep(time.Second)
-}