builder/docker: StepExport tests

builder/docker/driver.go

 package docker
 
+import (
+	"io"
+)
+
 // Driver is the interface that has to be implemented to communicate with
 // Docker. The Driver interface also allows the steps to be tested since
 // a mock driver can be shimmed in.
 type Driver interface {
+	// Export exports the container with the given ID to the given writer.
+	Export(id string, dst io.Writer) error
+
 	// Pull should pull down the given image.
 	Pull(image string) error
 

builder/docker/driver_docker.go

@@ -4,6 +4,7 @@ import (
 	"bytes"
 	"fmt"
 	"github.com/mitchellh/packer/packer"
+	"io"
 	"log"
 	"os/exec"
 	"strings"
@@ -13,6 +14,26 @@ type DockerDriver struct {
 	Ui packer.Ui
 }
 
+func (d *DockerDriver) Export(id string, dst io.Writer) error {
+	var stderr bytes.Buffer
+	cmd := exec.Command("docker", "export", id)
+	cmd.Stdout = dst
+	cmd.Stderr = &stderr
+
+	log.Printf("Exporting container: %s", id)
+	if err := cmd.Start(); err != nil {
+		return err
+	}
+
+	if err := cmd.Wait(); err != nil {
+		err = fmt.Errorf("Error exporting: %s\nStderr: %s",
+			err, stderr.String())
+		return err
+	}
+
+	return nil
+}
+
 func (d *DockerDriver) Pull(image string) error {
 	cmd := exec.Command("docker", "pull", image)
 	return runAndStream(cmd, d.Ui)

builder/docker/driver_mock.go

 package docker
 
+import (
+	"io"
+)
+
 // MockDriver is a driver implementation that can be used for tests.
 type MockDriver struct {
-	PullError  error
-	StartID    string
-	StartError error
-	StopError  error
-
-	PullCalled  bool
-	PullImage   string
-	StartCalled bool
-	StartConfig *ContainerConfig
-	StopCalled  bool
-	StopID      string
+	ExportReader io.Reader
+	ExportError  error
+	PullError    error
+	StartID      string
+	StartError   error
+	StopError    error
+
+	ExportCalled bool
+	ExportID     string
+	PullCalled   bool
+	PullImage    string
+	StartCalled  bool
+	StartConfig  *ContainerConfig
+	StopCalled   bool
+	StopID       string
+}
+
+func (d *MockDriver) Export(id string, dst io.Writer) error {
+	d.ExportCalled = true
+	d.ExportID = id
+
+	if d.ExportReader != nil {
+		_, err := io.Copy(dst, d.ExportReader)
+		if err != nil {
+			return err
+		}
+	}
+
+	return d.ExportError
 }
 
 func (d *MockDriver) Pull(image string) error {

builder/docker/step_export.go

 package docker
 
 import (
-	"bytes"
 	"fmt"
 	"github.com/mitchellh/multistep"
 	"github.com/mitchellh/packer/packer"
-	"log"
 	"os"
-	"os/exec"
 )
 
 // StepExport exports the container to a flat tar file.
@@ -15,14 +12,10 @@ type StepExport struct{}
 
 func (s *StepExport) Run(state multistep.StateBag) multistep.StepAction {
 	config := state.Get("config").(*Config)
+	driver := state.Get("driver").(Driver)
 	containerId := state.Get("container_id").(string)
 	ui := state.Get("ui").(packer.Ui)
 
-	ui.Say("Exporting the container")
-
-	// Args that we're going to pass to Docker
-	args := []string{"export", containerId}
-
 	// Open the file that we're going to write to
 	f, err := os.Create(config.ExportPath)
 	if err != nil {
@@ -31,30 +24,18 @@ func (s *StepExport) Run(state multistep.StateBag) multistep.StepAction {
 		ui.Error(err.Error())
 		return multistep.ActionHalt
 	}
-	defer f.Close()
 
-	// Export the thing, take stderr and point it to the file
-	var stderr bytes.Buffer
-	cmd := exec.Command("docker", args...)
-	cmd.Stdout = f
-	cmd.Stderr = &stderr
-
-	log.Printf("Starting container with args: %v", args)
-	if err := cmd.Start(); err != nil {
-		err := fmt.Errorf("Error exporting: %s", err)
-		state.Put("error", err)
-		ui.Error(err.Error())
-		return multistep.ActionHalt
-	}
+	ui.Say("Exporting the container")
+	if err := driver.Export(containerId, f); err != nil {
+		f.Close()
+		os.Remove(f.Name())
 
-	if err := cmd.Wait(); err != nil {
-		err := fmt.Errorf("Error exporting: %s\nStderr: %s",
-			err, stderr.String())
 		state.Put("error", err)
 		ui.Error(err.Error())
 		return multistep.ActionHalt
 	}
 
+	f.Close()
 	return multistep.ActionContinue
 }
 

builder/docker/step_export_test.go

+package docker
+
+import (
+	"bytes"
+	"errors"
+	"github.com/mitchellh/multistep"
+	"io/ioutil"
+	"os"
+	"testing"
+)
+
+func testStepExportState(t *testing.T) multistep.StateBag {
+	state := testState(t)
+	state.Put("container_id", "foo")
+	return state
+}
+
+func TestStepExport_impl(t *testing.T) {
+	var _ multistep.Step = new(StepExport)
+}
+
+func TestStepExport(t *testing.T) {
+	state := testStepExportState(t)
+	step := new(StepExport)
+	defer step.Cleanup(state)
+
+	// Create a tempfile for our output path
+	tf, err := ioutil.TempFile("", "packer")
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	tf.Close()
+	defer os.Remove(tf.Name())
+
+	config := state.Get("config").(*Config)
+	config.ExportPath = tf.Name()
+	driver := state.Get("driver").(*MockDriver)
+	driver.ExportReader = bytes.NewReader([]byte("data!"))
+
+	// run the step
+	if action := step.Run(state); action != multistep.ActionContinue {
+		t.Fatalf("bad action: %#v", action)
+	}
+
+	// verify we did the right thing
+	if !driver.ExportCalled {
+		t.Fatal("should've exported")
+	}
+	if driver.ExportID != "foo" {
+		t.Fatalf("bad: %#v", driver.ExportID)
+	}
+
+	// verify the data exported to the file
+	contents, err := ioutil.ReadFile(tf.Name())
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	if string(contents) != "data!" {
+		t.Fatalf("bad: %#v", string(contents))
+	}
+}
+
+func TestStepExport_error(t *testing.T) {
+	state := testStepExportState(t)
+	step := new(StepExport)
+	defer step.Cleanup(state)
+
+	// Create a tempfile for our output path
+	tf, err := ioutil.TempFile("", "packer")
+	if err != nil {
+		t.Fatalf("err: %s", err)
+	}
+	tf.Close()
+
+	if err := os.Remove(tf.Name()); err != nil {
+		t.Fatalf("err: %s", err)
+	}
+
+	config := state.Get("config").(*Config)
+	config.ExportPath = tf.Name()
+	driver := state.Get("driver").(*MockDriver)
+	driver.ExportError = errors.New("foo")
+
+	// run the step
+	if action := step.Run(state); action != multistep.ActionHalt {
+		t.Fatalf("bad action: %#v", action)
+	}
+
+	// verify we have an error
+	if _, ok := state.GetOk("error"); !ok {
+		t.Fatal("should have error")
+	}
+
+	// verify we didn't make that file
+	if _, err := os.Stat(tf.Name()); err == nil {
+		t.Fatal("export path shouldn't exist")
+	}
+}