diff --git a/helmexec/exec.go b/helmexec/exec.go
index d43670c3..00aabb88 100644
--- a/helmexec/exec.go
+++ b/helmexec/exec.go
@@ -3,9 +3,6 @@ package helmexec
 import (
 	"fmt"
 	"io"
-	"io/ioutil"
-	"os"
-	"os/exec"
 	"strings"
 )
 
@@ -14,15 +11,17 @@ const (
 )
 
 type execer struct {
+	runner      Runner
 	writer      io.Writer
 	kubeContext string
 	extra       []string
 }
 
-func NewHelmExec(writer io.Writer, kubeContext string) Interface {
+func New(writer io.Writer, kubeContext string) *execer {
 	return &execer{
 		writer:      writer,
 		kubeContext: kubeContext,
+		runner:      &ShellRunner{},
 	}
 }
 
@@ -84,12 +83,6 @@ func (helm *execer) DeleteRelease(name string) error {
 }
 
 func (helm *execer) exec(args ...string) ([]byte, error) {
-	dir, err := ioutil.TempDir("", "helmfile-exec")
-	if err != nil {
-		return nil, err
-	}
-	defer os.RemoveAll(dir)
-
 	cmdargs := args
 	if len(helm.extra) > 0 {
 		cmdargs = append(cmdargs, helm.extra...)
@@ -100,8 +93,5 @@ func (helm *execer) exec(args ...string) ([]byte, error) {
 	if helm.writer != nil {
 		helm.writer.Write([]byte(fmt.Sprintf("exec: helm %s\n", strings.Join(cmdargs, " "))))
 	}
-
-	cmd := exec.Command(command, cmdargs...)
-	cmd.Dir = dir
-	return cmd.CombinedOutput()
+	return helm.runner.Execute(command, cmdargs)
 }
diff --git a/helmexec/exec_test.go b/helmexec/exec_test.go
new file mode 100644
index 00000000..c7d3f13a
--- /dev/null
+++ b/helmexec/exec_test.go
@@ -0,0 +1,177 @@
+package helmexec
+
+import (
+	"bytes"
+	"io"
+	"reflect"
+	"testing"
+)
+
+// Mocking the command-line runner
+
+type mockRunner struct {
+	output []byte
+	err    error
+}
+
+func (mock *mockRunner) Execute(cmd string, args []string) ([]byte, error) {
+	return []byte{}, nil
+}
+
+func MockExecer(writer io.Writer, kubeContext string) *execer {
+	execer := New(writer, kubeContext)
+	execer.runner = &mockRunner{}
+	return execer
+}
+
+// Test methods
+
+func TestNewHelmExec(t *testing.T) {
+	buffer := bytes.NewBufferString("something")
+	helm := New(buffer, "dev")
+	if helm.kubeContext != "dev" {
+		t.Error("helmexec.New() - kubeContext")
+	}
+	if buffer.String() != "something" {
+		t.Error("helmexec.New() - changed buffer")
+	}
+	if len(helm.extra) != 0 {
+		t.Error("helmexec.New() - extra args not empty")
+	}
+}
+
+func Test_SetExtraArgs(t *testing.T) {
+	helm := New(new(bytes.Buffer), "dev")
+	helm.SetExtraArgs()
+	if len(helm.extra) != 0 {
+		t.Error("helmexec.SetExtraArgs() - passing no arguments should not change extra field")
+	}
+	helm.SetExtraArgs("foo")
+	if !reflect.DeepEqual(helm.extra, []string{"foo"}) {
+		t.Error("helmexec.SetExtraArgs() - one extra argument missing")
+	}
+	helm.SetExtraArgs("alpha", "beta")
+	if !reflect.DeepEqual(helm.extra, []string{"alpha", "beta"}) {
+		t.Error("helmexec.SetExtraArgs() - two extra arguments missing (overwriting the previous value)")
+	}
+}
+
+func Test_AddRepo(t *testing.T) {
+	var buffer bytes.Buffer
+	helm := MockExecer(&buffer, "dev")
+	helm.AddRepo("myRepo", "https://repo.example.com/", "cert.pem", "key.pem")
+	expected := "exec: helm repo add myRepo https://repo.example.com/ --cert-file cert.pem --key-file key.pem --kube-context dev\n"
+	if buffer.String() != expected {
+		t.Errorf("helmexec.AddRepo()\nactual = %v\nexpect = %v", buffer.String(), expected)
+	}
+
+	buffer.Reset()
+	helm.AddRepo("myRepo", "https://repo.example.com/", "", "")
+	expected = "exec: helm repo add myRepo https://repo.example.com/ --kube-context dev\n"
+	if buffer.String() != expected {
+		t.Errorf("helmexec.AddRepo()\nactual = %v\nexpect = %v", buffer.String(), expected)
+	}
+}
+
+func Test_UpdateRepo(t *testing.T) {
+	var buffer bytes.Buffer
+	helm := MockExecer(&buffer, "dev")
+	helm.UpdateRepo()
+	expected := "exec: helm repo update --kube-context dev\n"
+	if buffer.String() != expected {
+		t.Errorf("helmexec.UpdateRepo()\nactual = %v\nexpect = %v", buffer.String(), expected)
+	}
+}
+
+func Test_SyncRelease(t *testing.T) {
+	var buffer bytes.Buffer
+	helm := MockExecer(&buffer, "dev")
+	helm.SyncRelease("release", "chart", "--timeout 10", "--wait")
+	expected := "exec: helm upgrade --install release chart --timeout 10 --wait --kube-context dev\n"
+	if buffer.String() != expected {
+		t.Errorf("helmexec.SyncRelease()\nactual = %v\nexpect = %v", buffer.String(), expected)
+	}
+
+	buffer.Reset()
+	helm.SyncRelease("release", "chart")
+	expected = "exec: helm upgrade --install release chart --kube-context dev\n"
+	if buffer.String() != expected {
+		t.Errorf("helmexec.AddRepo()\nactual = %v\nexpect = %v", buffer.String(), expected)
+	}
+}
+
+func Test_DecryptSecret(t *testing.T) {
+	var buffer bytes.Buffer
+	helm := MockExecer(&buffer, "dev")
+	helm.DecryptSecret("secretName")
+	expected := "exec: helm secrets dec secretName --kube-context dev\n"
+	if buffer.String() != expected {
+		t.Errorf("helmexec.DecryptSecret()\nactual = %v\nexpect = %v", buffer.String(), expected)
+	}
+}
+
+func Test_DiffRelease(t *testing.T) {
+	var buffer bytes.Buffer
+	helm := MockExecer(&buffer, "dev")
+	helm.DiffRelease("release", "chart", "--timeout 10", "--wait")
+	expected := "exec: helm diff release chart --timeout 10 --wait --kube-context dev\n"
+	if buffer.String() != expected {
+		t.Errorf("helmexec.DiffRelease()\nactual = %v\nexpect = %v", buffer.String(), expected)
+	}
+
+	buffer.Reset()
+	helm.DiffRelease("release", "chart")
+	expected = "exec: helm diff release chart --kube-context dev\n"
+	if buffer.String() != expected {
+		t.Errorf("helmexec.DiffRelease()\nactual = %v\nexpect = %v", buffer.String(), expected)
+	}
+}
+
+func Test_DeleteRelease(t *testing.T) {
+	var buffer bytes.Buffer
+	helm := MockExecer(&buffer, "dev")
+	helm.DeleteRelease("release")
+	expected := "exec: helm delete --purge release --kube-context dev\n"
+	if buffer.String() != expected {
+		t.Errorf("helmexec.DeleteRelease()\nactual = %v\nexpect = %v", buffer.String(), expected)
+	}
+}
+
+func Test_exec(t *testing.T) {
+	var buffer bytes.Buffer
+	helm := MockExecer(&buffer, "")
+	helm.exec("version")
+	expected := "exec: helm version\n"
+	if buffer.String() != expected {
+		t.Errorf("helmexec.exec()\nactual = %v\nexpect = %v", buffer.String(), expected)
+	}
+
+	helm = MockExecer(nil, "dev")
+	ret, _ := helm.exec("diff")
+	if len(ret) != 0 {
+		t.Error("helmexec.exec() - expected empty return value")
+	}
+
+	buffer.Reset()
+	helm = MockExecer(&buffer, "dev")
+	helm.exec("diff", "release", "chart", "--timeout 10", "--wait")
+	expected = "exec: helm diff release chart --timeout 10 --wait --kube-context dev\n"
+	if buffer.String() != expected {
+		t.Errorf("helmexec.exec()\nactual = %v\nexpect = %v", buffer.String(), expected)
+	}
+
+	buffer.Reset()
+	helm.exec("version")
+	expected = "exec: helm version --kube-context dev\n"
+	if buffer.String() != expected {
+		t.Errorf("helmexec.exec()\nactual = %v\nexpect = %v", buffer.String(), expected)
+	}
+
+	buffer.Reset()
+	helm.SetExtraArgs("foo")
+	helm.exec("version")
+	expected = "exec: helm version foo --kube-context dev\n"
+	if buffer.String() != expected {
+		t.Errorf("helmexec.exec()\nactual = %v\nexpect = %v", buffer.String(), expected)
+	}
+}
diff --git a/helmexec/runner.go b/helmexec/runner.go
new file mode 100644
index 00000000..b1f5a7fa
--- /dev/null
+++ b/helmexec/runner.go
@@ -0,0 +1,30 @@
+package helmexec
+
+import (
+	"io/ioutil"
+	"os"
+	"os/exec"
+)
+
+const (
+	tmpPrefix = "helmfile-"
+	tmpSuffix = "-exec"
+)
+
+type Runner interface {
+	Execute(cmd string, args []string) ([]byte, error)
+}
+
+type ShellRunner struct{}
+
+func (shell ShellRunner) Execute(cmd string, args []string) ([]byte, error) {
+	dir, err := ioutil.TempDir("", tmpPrefix+cmd+tmpSuffix)
+	if err != nil {
+		return nil, err
+	}
+	defer os.RemoveAll(dir)
+
+	preparedCmd := exec.Command(cmd, args...)
+	preparedCmd.Dir = dir
+	return preparedCmd.CombinedOutput()
+}
diff --git a/main.go b/main.go
index 2d7e69cc..5d036d0d 100644
--- a/main.go
+++ b/main.go
@@ -278,7 +278,7 @@ func before(c *cli.Context) (*state.HelmState, helmexec.Interface, error) {
 		clean(st, errs)
 	}()
 
-	return st, helmexec.NewHelmExec(writer, kubeContext), nil
+	return st, helmexec.New(writer, kubeContext), nil
 }
 
 func clean(state *state.HelmState, errs []error) error {