imap: add Authenticatable interface

Used by Authenticator, mainly to allow mocking for testing.

imap/authenticator.go

@@ -19,7 +19,6 @@
 package imap
 
 import (
-	"github.com/emersion/go-imap/client"
 	"github.com/emersion/go-sasl"
 	"golang.org/x/oauth2"
 )
@@ -33,7 +32,7 @@ func NewNormalAuthenticator(username string, password string) Authenticator {
 	return &plainAuthenticator{username: username, password: password}
 }
 
-func (a *plainAuthenticator) Authenticate(c *client.Client) error {
+func (a *plainAuthenticator) Authenticate(c Authenticatable) error {
 	return c.Login(a.username, a.password)
 }
 
@@ -45,7 +44,7 @@ func NewSASLAuthenticator(client sasl.Client) Authenticator {
 	return &saslAuthenticator{client: client}
 }
 
-func (a *saslAuthenticator) Authenticate(c *client.Client) error {
+func (a *saslAuthenticator) Authenticate(c Authenticatable) error {
 	return c.Authenticate(a.client)
 }
 
@@ -61,7 +60,7 @@ func NewOAuthBearerAuthenticator(username string, source oauth2.TokenSource) Aut
 	}
 }
 
-func (a *oauthBearerAuthenticator) Authenticate(c *client.Client) error {
+func (a *oauthBearerAuthenticator) Authenticate(c Authenticatable) error {
 	tok, err := a.source.Token()
 	if err != nil {
 		return err

imap/types.go

@@ -22,6 +22,8 @@ import (
 	"crypto/tls"
 	"time"
 
+	"github.com/emersion/go-sasl"
+
 	"github.com/emersion/go-imap"
 	"github.com/emersion/go-imap/client"
 )
@@ -48,10 +50,17 @@ type Client interface {
 	FlagQuit()
 }
 
+// Authenticatable is the minimal set of functions that are
+// used by an Authenticator. This is mainly to assist with mocking.
+type Authenticatable interface {
+	Login(username, password string) error
+	Authenticate(auth sasl.Client) error
+}
+
 // Authenticator provides a common interface to authenticate via
 // username/password and SASL.
 type Authenticator interface {
-	Authenticate(c *client.Client) error
+	Authenticate(a Authenticatable) error
 }
 
 // ConnectionConfig contains the base configuration required