test(coderd/notifications): fix data race in tests and smpttest (#15304)

coderd/notifications/dispatch/smtptest/server.go

@@ -5,6 +5,7 @@ import (
 	_ "embed"
 	"io"
 	"net"
+	"slices"
 	"sync"
 	"time"
 
@@ -53,11 +54,22 @@ func (b *Backend) NewSession(c *smtp.Conn) (smtp.Session, error) {
 	return &Session{conn: c, backend: b}, nil
 }
 
+// LastMessage returns a copy of the last message received by the
+// backend.
 func (b *Backend) LastMessage() *Message {
-	return b.lastMsg
+	b.mu.Lock()
+	defer b.mu.Unlock()
+	if b.lastMsg == nil {
+		return nil
+	}
+	clone := *b.lastMsg
+	clone.To = slices.Clone(b.lastMsg.To)
+	return &clone
 }
 
 func (b *Backend) Reset() {
+	b.mu.Lock()
+	defer b.mu.Unlock()
 	b.lastMsg = nil
 }
 
@@ -84,6 +96,9 @@ func (s *Session) Auth(mech string) (sasl.Server, error) {
 	switch mech {
 	case sasl.Plain:
 		return sasl.NewPlainServer(func(identity, username, password string) error {
+			s.backend.mu.Lock()
+			defer s.backend.mu.Unlock()
+
 			s.backend.lastMsg.Identity = identity
 			s.backend.lastMsg.Username = username
 			s.backend.lastMsg.Password = password
@@ -102,6 +117,9 @@ func (s *Session) Auth(mech string) (sasl.Server, error) {
 		}), nil
 	case sasl.Login:
 		return sasl.NewLoginServer(func(username, password string) error {
+			s.backend.mu.Lock()
+			defer s.backend.mu.Unlock()
+
 			s.backend.lastMsg.Username = username
 			s.backend.lastMsg.Password = password
 

coderd/notifications/notifications_test.go

@@ -1253,12 +1253,12 @@ func TestNotificationTemplates_Golden(t *testing.T) {
 				// Spin up the mock webhook server
 				var body []byte
 				var readErr error
-				var webhookReceived bool
+				webhookReceived := make(chan struct{})
 				server := httptest.NewServer(http.HandlerFunc(func(w http.ResponseWriter, r *http.Request) {
 					w.WriteHeader(http.StatusOK)
 
 					body, readErr = io.ReadAll(r.Body)
-					webhookReceived = true
+					close(webhookReceived)
 				}))
 				t.Cleanup(server.Close)
 
@@ -1302,12 +1302,11 @@ func TestNotificationTemplates_Golden(t *testing.T) {
 				)
 				require.NoError(t, err)
 
-				require.Eventually(t, func() bool {
-					return webhookReceived
-				}, testutil.WaitShort, testutil.IntervalFast)
-
-				require.NoError(t, err)
-
+				select {
+				case <-time.After(testutil.WaitShort):
+					require.Fail(t, "timed out waiting for webhook to be received")
+				case <-webhookReceived:
+				}
 				// Handle the body that was read in the http server here.
 				// We need to do it here because we can't call require.* in a separate goroutine, such as the http server handler
 				require.NoError(t, readErr)