diff --git a/dialer.go b/dialer.go
index 8a62a997..3d9216a5 100644
--- a/dialer.go
+++ b/dialer.go
@@ -107,6 +107,7 @@ type connectionInfoCache interface {
 	ConnectionInfo(context.Context) (cloudsql.ConnectionInfo, error)
 	UpdateRefresh(*bool)
 	ForceRefresh()
+	UseIAMAuthN() bool
 	io.Closer
 }
 
diff --git a/internal/cloudsql/instance.go b/internal/cloudsql/instance.go
index f8e44b3b..caabc43a 100644
--- a/internal/cloudsql/instance.go
+++ b/internal/cloudsql/instance.go
@@ -165,6 +165,11 @@ func (i *RefreshAheadCache) Close() error {
 	return nil
 }
 
+// UseIAMAuthN returns true if this dialer is using IAM AuthN
+func (i *RefreshAheadCache) UseIAMAuthN() bool {
+	return i.useIAMAuthNDial
+}
+
 // ConnectionInfo contains all necessary information to connect securely to the
 // server-side Proxy running on a Cloud SQL instance.
 type ConnectionInfo struct {
diff --git a/internal/cloudsql/lazy.go b/internal/cloudsql/lazy.go
index 5b65b3b9..ef490c27 100644
--- a/internal/cloudsql/lazy.go
+++ b/internal/cloudsql/lazy.go
@@ -141,3 +141,8 @@ func (c *LazyRefreshCache) ForceRefresh() {
 func (c *LazyRefreshCache) Close() error {
 	return nil
 }
+
+// UseIAMAuthN returns true if this dialer is using IAM AuthN
+func (c *LazyRefreshCache) UseIAMAuthN() bool {
+	return c.useIAMAuthNDial
+}
diff --git a/internal/mock/cloudsql.go b/internal/mock/cloudsql.go
index 27fc80a3..dc341240 100644
--- a/internal/mock/cloudsql.go
+++ b/internal/mock/cloudsql.go
@@ -325,7 +325,7 @@ func StartServerProxy(t *testing.T, i FakeCSQLInstance) func() {
 	if err != nil {
 		t.Fatalf("failed to create X.509 Key Pair: %v", err)
 	}
-	ln, err := tls.Listen("tcp", ":3307", &tls.Config{
+	ln, err := tls.Listen("tcp", fmt.Sprintf(":3307"), &tls.Config{
 		Certificates: []tls.Certificate{serverCert},
 	})
 	if err != nil {