Add tests for Msg.HasSendError method.

Introduce several unit tests for the Msg.HasSendError function to ensure its correct behavior under different conditions like unsent messages, failed deliveries, and temporary errors. This enhances the validation of message error states within the system.

msg_test.go

@@ -5816,6 +5816,227 @@ func TestMsg_UpdateReader(t *testing.T) {
 	})
 }
 
+func TestMsg_HasSendError(t *testing.T) {
+	t.Run("HasSendError on unsent message", func(t *testing.T) {
+		message := testMessage(t)
+		if message.HasSendError() {
+			t.Error("HasSendError on unsent message should return false")
+		}
+	})
+	t.Run("HasSendError on sent message", func(t *testing.T) {
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+		PortAdder.Add(1)
+		serverPort := int(TestServerPortBase + PortAdder.Load())
+		featureSet := "250-8BITMIME\r\n250-DSN\r\n250 SMTPUTF8"
+		go func() {
+			if err := simpleSMTPServer(ctx, t, &serverProps{
+				FeatureSet: featureSet,
+				ListenPort: serverPort,
+			}); err != nil {
+				t.Errorf("failed to start test server: %s", err)
+				return
+			}
+		}()
+		time.Sleep(time.Millisecond * 30)
+
+		client, err := NewClient(DefaultHost, WithPort(serverPort), WithTLSPolicy(NoTLS))
+		if err != nil {
+			t.Fatalf("failed to create new client: %s", err)
+		}
+
+		message := testMessage(t)
+		if err = client.DialAndSend(message); err != nil {
+			var netErr net.Error
+			if errors.As(err, &netErr) && netErr.Timeout() {
+				t.Skip("failed to connect to the test server due to timeout")
+			}
+			t.Fatalf("failed to connect to test server: %s", err)
+		}
+		t.Cleanup(func() {
+			if err := client.Close(); err != nil {
+				t.Errorf("failed to close client: %s", err)
+			}
+		})
+
+		if message.HasSendError() {
+			t.Error("HasSendError on sent message should return false")
+		}
+	})
+	t.Run("HasSendError on failed message delivery", func(t *testing.T) {
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+		PortAdder.Add(1)
+		serverPort := int(TestServerPortBase + PortAdder.Load())
+		featureSet := "250-8BITMIME\r\n250-DSN\r\n250 SMTPUTF8"
+		go func() {
+			if err := simpleSMTPServer(ctx, t, &serverProps{
+				FailOnDataClose: true,
+				FeatureSet:      featureSet,
+				ListenPort:      serverPort,
+			}); err != nil {
+				t.Errorf("failed to start test server: %s", err)
+				return
+			}
+		}()
+		time.Sleep(time.Millisecond * 30)
+
+		client, err := NewClient(DefaultHost, WithPort(serverPort), WithTLSPolicy(NoTLS))
+		if err != nil {
+			t.Fatalf("failed to create new client: %s", err)
+		}
+
+		message := testMessage(t)
+		if err = client.DialAndSend(message); err == nil {
+			t.Error("message delivery was supposed to fail on data close")
+		}
+		if !message.HasSendError() {
+			t.Error("HasSendError on failed message delivery should return true")
+		}
+	})
+	t.Run("HasSendError on failed message with SendError", func(t *testing.T) {
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+		PortAdder.Add(1)
+		serverPort := int(TestServerPortBase + PortAdder.Load())
+		featureSet := "250-8BITMIME\r\n250-DSN\r\n250 SMTPUTF8"
+		go func() {
+			if err := simpleSMTPServer(ctx, t, &serverProps{
+				FailOnDataClose: true,
+				FeatureSet:      featureSet,
+				ListenPort:      serverPort,
+			}); err != nil {
+				t.Errorf("failed to start test server: %s", err)
+				return
+			}
+		}()
+		time.Sleep(time.Millisecond * 30)
+
+		client, err := NewClient(DefaultHost, WithPort(serverPort), WithTLSPolicy(NoTLS))
+		if err != nil {
+			t.Fatalf("failed to create new client: %s", err)
+		}
+
+		message := testMessage(t)
+		if err = client.DialAndSend(message); err == nil {
+			t.Error("message delivery was supposed to fail on data close")
+		}
+		if !message.HasSendError() {
+			t.Fatal("HasSendError on failed message delivery should return true")
+		}
+		if message.SendError() == nil {
+			t.Fatal("SendError on failed message delivery should return SendErr")
+		}
+		var sendErr *SendError
+		if !errors.As(message.SendError(), &sendErr) {
+			t.Fatal("expected SendError to return a SendError type")
+		}
+	})
+	t.Run("HasSendError with SendErrorIsTemp", func(t *testing.T) {
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+		PortAdder.Add(1)
+		serverPort := int(TestServerPortBase + PortAdder.Load())
+		featureSet := "250-8BITMIME\r\n250-DSN\r\n250 SMTPUTF8"
+		go func() {
+			if err := simpleSMTPServer(ctx, t, &serverProps{
+				FailOnDataClose: true,
+				FeatureSet:      featureSet,
+				ListenPort:      serverPort,
+			}); err != nil {
+				t.Errorf("failed to start test server: %s", err)
+				return
+			}
+		}()
+		time.Sleep(time.Millisecond * 30)
+
+		client, err := NewClient(DefaultHost, WithPort(serverPort), WithTLSPolicy(NoTLS))
+		if err != nil {
+			t.Fatalf("failed to create new client: %s", err)
+		}
+
+		message := testMessage(t)
+		if err = client.DialAndSend(message); err == nil {
+			t.Error("message delivery was supposed to fail on data close")
+		}
+		if !message.HasSendError() {
+			t.Error("HasSendError on failed message delivery should return true")
+		}
+		if message.SendErrorIsTemp() {
+			t.Error("SendErrorIsTemp on hard failed message delivery should return false")
+		}
+	})
+	t.Run("HasSendError with SendErrorIsTemp on temp error", func(t *testing.T) {
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+		PortAdder.Add(1)
+		serverPort := int(TestServerPortBase + PortAdder.Load())
+		featureSet := "250-8BITMIME\r\n250-DSN\r\n250 SMTPUTF8"
+		go func() {
+			if err := simpleSMTPServer(ctx, t, &serverProps{
+				FailTemp:   true,
+				FeatureSet: featureSet,
+				ListenPort: serverPort,
+			}); err != nil {
+				t.Errorf("failed to start test server: %s", err)
+				return
+			}
+		}()
+		time.Sleep(time.Millisecond * 30)
+
+		client, err := NewClient(DefaultHost, WithPort(serverPort), WithTLSPolicy(NoTLS))
+		if err != nil {
+			t.Fatalf("failed to create new client: %s", err)
+		}
+
+		message := testMessage(t)
+		if err = client.DialAndSend(message); err == nil {
+			t.Error("message delivery was supposed to fail on data close")
+		}
+		if !message.HasSendError() {
+			t.Error("HasSendError on failed message delivery should return true")
+		}
+		if !message.SendErrorIsTemp() {
+			t.Error("SendErrorIsTemp on temp failed message delivery should return true")
+		}
+	})
+	t.Run("HasSendError with not a SendErr", func(t *testing.T) {
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+		PortAdder.Add(1)
+		serverPort := int(TestServerPortBase + PortAdder.Load())
+		featureSet := "250-8BITMIME\r\n250-DSN\r\n250 SMTPUTF8"
+		go func() {
+			if err := simpleSMTPServer(ctx, t, &serverProps{
+				FailTemp:   true,
+				FeatureSet: featureSet,
+				ListenPort: serverPort,
+			}); err != nil {
+				t.Errorf("failed to start test server: %s", err)
+				return
+			}
+		}()
+		time.Sleep(time.Millisecond * 30)
+
+		client, err := NewClient(DefaultHost, WithPort(serverPort), WithTLSPolicy(NoTLS))
+		if err != nil {
+			t.Fatalf("failed to create new client: %s", err)
+		}
+
+		message := testMessage(t)
+		if err = client.DialAndSend(message); err == nil {
+			t.Error("message delivery was supposed to fail on data close")
+		}
+		message.sendError = errors.New("not a SendErr")
+		if !message.HasSendError() {
+			t.Error("HasSendError with not a SendErr should still return true")
+		}
+		if message.SendErrorIsTemp() {
+			t.Error("SendErrorIsTemp on not a SendErr should return false")
+		}
+	})
+}
+
 /*
 // TestMsg_hasAlt tests the hasAlt() method of the Msg