notifications: Fix flaky SMTP tests (#90801)

Signed-off-by: Dave Henderson <dave.henderson@grafana.com>

pkg/services/notifications/smtp_test.go

@@ -10,6 +10,7 @@ import (
 	"net/textproto"
 	"strings"
 	"testing"
+	"time"
 
 	smtpmock "github.com/mocktools/go-smtp-mock/v2"
 	"github.com/stretchr/testify/assert"
@@ -150,10 +151,9 @@ func TestSmtpDialer(t *testing.T) {
 }
 
 func TestSmtpSend(t *testing.T) {
-	// Test is currently very flaky. Skipping it for now.
-	t.Skip()
 	srv := smtpmock.New(smtpmock.ConfigurationAttr{
 		MultipleRcptto: true,
+		HostAddress:    "127.0.0.1",
 	})
 	require.NoError(t, srv.Start())
 	defer func() { _ = srv.Stop() }()
@@ -183,6 +183,8 @@ func TestSmtpSend(t *testing.T) {
 		require.NoError(t, err)
 		require.Equal(t, 1, count)
 
+		// workaround for https://github.com/mocktools/go-smtp-mock/issues/181
+		time.Sleep(1 * time.Millisecond)
 		messages := srv.MessagesAndPurge()
 		require.Len(t, messages, 1)
 		sentMsg := messages[0]
@@ -233,6 +235,8 @@ func TestSmtpSend(t *testing.T) {
 		require.NoError(t, err)
 		require.Equal(t, 1, count)
 
+		// workaround for https://github.com/mocktools/go-smtp-mock/issues/181
+		time.Sleep(1 * time.Millisecond)
 		messages := srv.MessagesAndPurge()
 		require.Len(t, messages, 1)
 		sentMsg := messages[0]
@@ -292,6 +296,8 @@ func TestSmtpSend(t *testing.T) {
 		require.NoError(t, err)
 		require.Equal(t, 3, count)
 
+		// workaround for https://github.com/mocktools/go-smtp-mock/issues/181
+		time.Sleep(1 * time.Millisecond)
 		messages := srv.MessagesAndPurge()
 		require.Len(t, messages, 3)