diff --git a/config/auth.go b/config/auth.go
index 9a07d41ec..2c0e8b9af 100644
--- a/config/auth.go
+++ b/config/auth.go
@@ -16,26 +16,8 @@ type AuthConfigData struct {
 }
 
 func StoreAuth(user *users.User) error {
-	// Check ~/.config/scalingo
-	if _, err := os.Stat(C.ConfigDir); err != nil {
-		if err, ok := err.(*os.PathError); ok {
-			if err := os.MkdirAll(C.ConfigDir, 0755); err != nil {
-				return errgo.Mask(err, errgo.Any)
-			}
-		} else {
-			return errgo.Notef(err, "error reaching config directory")
-		}
-	}
-
-	var authConfig AuthConfigData
-	authConfig.AuthConfigPerHost = make(map[string]*users.User)
-	content, err := ioutil.ReadFile(C.AuthFile)
-	if err == nil {
-		err = json.Unmarshal(content, &authConfig)
-		if err != nil {
-			return errgo.Mask(err)
-		}
-	} else if err != nil && !os.IsNotExist(err) {
+	authConfig, err := existingAuth()
+	if err != nil {
 		return errgo.Mask(err)
 	}
 
@@ -76,3 +58,17 @@ func LoadAuth() (*users.User, error) {
 		return user, nil
 	}
 }
+
+func existingAuth() (*AuthConfigData, error) {
+	authConfig := &AuthConfigData{}
+	content, err := ioutil.ReadFile(C.AuthFile)
+	if err == nil {
+		// We don't care of the error
+		json.Unmarshal(content, &authConfig)
+	} else if os.IsNotExist(err) {
+		authConfig.AuthConfigPerHost = make(map[string]*users.User)
+	} else {
+		return nil, errgo.Mask(err)
+	}
+	return authConfig, nil
+}
diff --git a/config/auth_test.go b/config/auth_test.go
new file mode 100644
index 000000000..ab56818c3
--- /dev/null
+++ b/config/auth_test.go
@@ -0,0 +1,106 @@
+package config
+
+import (
+	"reflect"
+	"testing"
+
+	"github.com/Scalingo/cli/users"
+)
+
+var (
+	u = &users.User{
+		Email:     "test@example.com",
+		Username:  "test",
+		AuthToken: "0123456789",
+	}
+)
+
+func TestStoreAuth(t *testing.T) {
+	// First creation
+	err := StoreAuth(u)
+	if err != nil {
+		t.Error("%v should be nil", err)
+	}
+	clean()
+
+	// Rewrite over an existing file
+	err = StoreAuth(u)
+	if err != nil {
+		t.Error("%v should be nil", err)
+	}
+	err = StoreAuth(u)
+	if err != nil {
+		t.Error("%v should be nil", err)
+	}
+	clean()
+
+	// Add an additional api url
+	err = StoreAuth(u)
+	if err != nil {
+		t.Error("%v should be nil", err)
+	}
+	C.apiHost = "scalingo2.dev"
+	err = StoreAuth(u)
+	if err != nil {
+		t.Error("%v should be nil", err)
+	}
+	clean()
+}
+
+func TestLoadAuth(t *testing.T) {
+	// Load without Store should return nil User
+	u, err := LoadAuth()
+	if err != nil {
+		t.Error("%v should be nil", err)
+	}
+	if u != nil {
+		t.Error("%v should be nil", u)
+	}
+
+	// Load after storage of credentials
+	err = StoreAuth(u)
+	if err != nil {
+		t.Error("%v should be nil", err)
+	}
+	uLoad, err := LoadAuth()
+	if err != nil {
+		t.Error("%v should be nil", err)
+	}
+	if !reflect.DeepEqual(uLoad, u) {
+		t.Error("want %v, got %v", u, uLoad)
+	}
+
+	clean()
+}
+
+func TestExistingAuth(t *testing.T) {
+	// Before any auth
+	auth, err := existingAuth()
+	if err != nil {
+		t.Error("%v should be nil", err)
+	}
+	if len(auth.AuthConfigPerHost) > 0 {
+		t.Error("want auth.AuthConfigPerHost = [], got %v", auth.AuthConfigPerHost)
+	}
+	if !auth.LastUpdate.IsZero() {
+		t.Error("auth should never have been updated: %v", auth.LastUpdate)
+	}
+
+	// After one auth
+	err = StoreAuth(u)
+	if err != nil {
+		t.Error("%v should be nil", err)
+	}
+	auth, err = existingAuth()
+	if err != nil {
+		t.Error("%v should be nil", err)
+	}
+	if len(auth.AuthConfigPerHost) != 1 {
+		t.Error("want len(auth.AuthConfigPerHost) = 1, got %v", auth.AuthConfigPerHost)
+	}
+	if auth.LastUpdate.IsZero() {
+		t.Error("auth should have been updated: %v", auth.LastUpdate)
+	}
+
+	clean()
+}
diff --git a/config/config.go b/config/config.go
index a70582327..664a7398c 100644
--- a/config/config.go
+++ b/config/config.go
@@ -7,6 +7,7 @@ import (
 	"net/url"
 	"os"
 	"path/filepath"
+	"runtime"
 	"strings"
 
 	"github.com/Scalingo/envconfig"
diff --git a/config/config_test.go b/config/config_test.go
new file mode 100644
index 000000000..bdb424758
--- /dev/null
+++ b/config/config_test.go
@@ -0,0 +1,18 @@
+package config
+
+import "os"
+
+var (
+	testConfig = Config{
+		apiHost:  "scalingo.dev",
+		AuthFile: "/tmp/test-scalingo-auth",
+	}
+)
+
+func init() {
+	C = testConfig
+}
+
+func clean() {
+	os.Remove(testConfig.AuthFile)
+}