Add integration tests for invalid host and HELO failure

Add test cases to validate client behavior on connecting with an invalid host and encountering a HELO failure. This helps ensure the client handles these error scenarios correctly, maintaining robustness and reliability.

client_test.go

@@ -1647,6 +1647,23 @@ func TestClient_DialWithContext(t *testing.T) {
 			t.Fatalf("client has no connection")
 		}
 	})
+	t.Run("fail on invalid host", func(t *testing.T) {
+		ctxDial, cancelDial := context.WithTimeout(ctx, time.Millisecond*500)
+		t.Cleanup(cancelDial)
+
+		client, err := NewClient(DefaultHost, WithPort(serverPort), WithTLSPolicy(NoTLS))
+		if err != nil {
+			t.Fatalf("failed to create new client: %s", err)
+		}
+		client.host = "invalid.addr"
+
+		if err = client.DialWithContext(ctxDial); err == nil {
+			t.Errorf("client with invalid host should fail")
+		}
+		if client.smtpClient != nil {
+			t.Errorf("client with invalid host should not have a smtp client")
+		}
+	})
 	t.Run("fail on base port and fallback", func(t *testing.T) {
 		ctxDial, cancelDial := context.WithTimeout(ctx, time.Millisecond*500)
 		t.Cleanup(cancelDial)
@@ -1701,119 +1718,48 @@ func TestClient_DialWithContext(t *testing.T) {
 			t.Errorf("logAuthData not working, no authentication info found in logs")
 		}
 	})
+	t.Run("connect should fail on HELO", func(t *testing.T) {
+		ctx, cancel := context.WithCancel(context.Background())
+		defer cancel()
+		PortAdder.Add(1)
+		failServerPort := int(TestServerPortBase + PortAdder.Load())
+		failFeatureSet := "250-AUTH PLAIN\r\n250-8BITMIME\r\n250-DSN\r\n250 SMTPUTF8"
+		go func() {
+			if err := simpleSMTPServer(ctx, &serverProps{
+				FailOnHelo: true,
+				FeatureSet: failFeatureSet,
+				ListenPort: failServerPort,
+			}); err != nil {
+				t.Errorf("failed to start test server: %s", err)
+				return
+			}
+		}()
+		time.Sleep(time.Millisecond * 300)
+
+		ctxDial, cancelDial := context.WithTimeout(ctx, time.Millisecond*500)
+		t.Cleanup(cancelDial)
+
+		client, err := NewClient(DefaultHost, WithPort(failServerPort), WithTLSPolicy(NoTLS))
+		if err != nil {
+			t.Fatalf("failed to create new client: %s", err)
+		}
+		if err = client.DialWithContext(ctxDial); err == nil {
+			t.Fatalf("connection was supposed to fail, but didn't")
+		}
+		if client.smtpClient == nil {
+			t.Fatalf("client has no smtp client")
+		}
+		if !client.smtpClient.HasConnection() {
+			t.Errorf("client has no connection")
+		}
+	})
+	// TODO: Implement tests for TLS/SSL and custom DialCtxFunc
 }
 
 /*
 
 
 
-// TestClient_DialWithContext tests the DialWithContext method for the Client object
-func TestClient_DialWithContext(t *testing.T) {
-	c, err := getTestConnection(true)
-	if err != nil {
-		t.Skipf("failed to create test client: %s. Skipping tests", err)
-	}
-	ctx := context.Background()
-	if err = c.DialWithContext(ctx); err != nil {
-		t.Errorf("failed to dial with context: %s", err)
-		return
-	}
-	if c.smtpClient == nil {
-		t.Errorf("DialWithContext didn't fail but no SMTP client found.")
-		return
-	}
-	if !c.smtpClient.HasConnection() {
-		t.Errorf("DialWithContext didn't fail but no connection found.")
-	}
-	if err := c.Close(); err != nil {
-		t.Errorf("failed to close connection: %s", err)
-	}
-}
-
-// TestClient_DialWithContext_Fallback tests the Client.DialWithContext method with the fallback
-// port functionality
-func TestClient_DialWithContext_Fallback(t *testing.T) {
-	c, err := getTestConnectionNoTestPort(true)
-	if err != nil {
-		t.Skipf("failed to create test client: %s. Skipping tests", err)
-	}
-	c.SetTLSPortPolicy(TLSOpportunistic)
-	c.port = 999
-	ctx := context.Background()
-	if err = c.DialWithContext(ctx); err != nil {
-		t.Errorf("failed to dial with context: %s", err)
-		return
-	}
-	if c.smtpClient == nil {
-		t.Errorf("DialWithContext didn't fail but no SMTP client found.")
-		return
-	}
-	if !c.smtpClient.HasConnection() {
-		t.Errorf("DialWithContext didn't fail but no connection found.")
-	}
-	if err = c.Close(); err != nil {
-		t.Errorf("failed to close connection: %s", err)
-	}
-
-	c.port = 999
-	c.fallbackPort = 999
-	if err = c.DialWithContext(ctx); err == nil {
-		t.Error("dial with context was supposed to fail, but didn't")
-		return
-	}
-}
-
-// TestClient_DialWithContext_Debug tests the DialWithContext method for the Client object with debug
-// logging enabled on the SMTP client
-func TestClient_DialWithContext_Debug(t *testing.T) {
-	c, err := getTestClient(true)
-	if err != nil {
-		t.Skipf("failed to create test client: %s. Skipping tests", err)
-	}
-	ctx := context.Background()
-	if err = c.DialWithContext(ctx); err != nil {
-		t.Errorf("failed to dial with context: %s", err)
-		return
-	}
-	if c.smtpClient == nil {
-		t.Errorf("DialWithContext didn't fail but no SMTP client found.")
-		return
-	}
-	if !c.smtpClient.HasConnection() {
-		t.Errorf("DialWithContext didn't fail but no connection found.")
-	}
-	c.SetDebugLog(true)
-	if err = c.Close(); err != nil {
-		t.Errorf("failed to close connection: %s", err)
-	}
-}
-
-// TestClient_DialWithContext_Debug_custom tests the DialWithContext method for the Client
-// object with debug logging enabled and a custom logger on the SMTP client
-func TestClient_DialWithContext_Debug_custom(t *testing.T) {
-	c, err := getTestClient(true)
-	if err != nil {
-		t.Skipf("failed to create test client: %s. Skipping tests", err)
-	}
-	ctx := context.Background()
-	if err = c.DialWithContext(ctx); err != nil {
-		t.Errorf("failed to dial with context: %s", err)
-		return
-	}
-	if c.smtpClient == nil {
-		t.Errorf("DialWithContext didn't fail but no SMTP client found.")
-		return
-	}
-	if !c.smtpClient.HasConnection() {
-		t.Errorf("DialWithContext didn't fail but no connection found.")
-	}
-	c.SetDebugLog(true)
-	c.SetLogger(log.New(os.Stderr, log.LevelDebug))
-	if err = c.Close(); err != nil {
-		t.Errorf("failed to close connection: %s", err)
-	}
-}
-
 // TestClient_DialWithContextInvalidHost tests the DialWithContext method with intentional breaking
 // for the Client object
 func TestClient_DialWithContextInvalidHost(t *testing.T) {
@@ -3685,8 +3631,9 @@ func parseJSONLog(t *testing.T, buf *bytes.Buffer) logData {
 }
 
 type serverProps struct {
-	FailOnReset bool
+	FailOnHelo  bool
 	FailOnQuit  bool
+	FailOnReset bool
 	FeatureSet  string
 	ListenPort  int
 }
@@ -3762,6 +3709,10 @@ func handleTestServerConnection(connection net.Conn, props *serverProps) {
 		fmt.Printf("expected EHLO, got %q", data)
 		return
 	}
+	if props.FailOnHelo {
+		_ = writeLine("500 5.5.2 Error: fail on HELO")
+		return
+	}
 	if err = writeLine("250-localhost.localdomain\r\n" + props.FeatureSet); err != nil {
 		return
 	}