packer/plugin: error if command can't start

packer/plugin/command.go

@@ -10,7 +10,7 @@ import (
 	"time"
 )
 
-func Command(cmd *exec.Cmd) packer.Command {
+func Command(cmd *exec.Cmd) (result packer.Command, err error) {
 	env := []string{
 		"PACKER_PLUGIN_MIN_PORT=10000",
 		"PACKER_PLUGIN_MAX_PORT=25000",
@@ -19,7 +19,10 @@ func Command(cmd *exec.Cmd) packer.Command {
 	out := new(bytes.Buffer)
 	cmd.Env = append(cmd.Env, env...)
 	cmd.Stdout = out
-	cmd.Start()
+	err = cmd.Start()
+	if err != nil {
+		return
+	}
 
 	// TODO: timeout
 	// TODO: check that command is even running
@@ -39,5 +42,6 @@ func Command(cmd *exec.Cmd) packer.Command {
 		panic(err)
 	}
 
-	return packrpc.Command(client)
+	result = packrpc.Command(client)
+	return
 }

packer/plugin/command_test.go

+package plugin
+
+import (
+	"cgl.tideland.biz/asserts"
+	"os/exec"
+	"testing"
+)
+
+func TestCommand_NoExist(t *testing.T) {
+	assert := asserts.NewTestingAsserts(t, true)
+
+	_, err := Command(exec.Command("i-should-never-ever-ever-exist"))
+	assert.NotNil(err, "should have an error")
+}
+
+func TestCommand_Good(t *testing.T) {
+	assert := asserts.NewTestingAsserts(t, true)
+
+	command, err := Command(helperProcess("command"))
+	assert.Nil(err, "should start command properly")
+
+	result := command.Synopsis()
+	assert.Equal(result, "1", "should return result")
+}

packer/plugin/plugin_test.go

 package plugin
 
 import (
-	"cgl.tideland.biz/asserts"
 	"github.com/mitchellh/packer/packer"
 	"os"
 	"os/exec"
@@ -32,15 +31,6 @@ func helperProcess(s... string) *exec.Cmd {
 	return cmd
 }
 
-func TestClient(t *testing.T) {
-	assert := asserts.NewTestingAsserts(t, true)
-
-	command := Command(helperProcess("command"))
-	result := command.Synopsis()
-
-	assert.Equal(result, "1", "should return result")
-}
-
 // This is not a real test. This is just a helper process kicked off by
 // tests.
 func TestHelperProcess(*testing.T) {