diff --git a/ui/src/main.rs b/ui/src/main.rs
index c516ea0..54b77d9 100644
--- a/ui/src/main.rs
+++ b/ui/src/main.rs
@@ -336,6 +336,9 @@ impl ChessApp {
                     ServerMessage2::UIUpdate { fen } => {
                         info!("Board updated with FEN: {}", fen);
                         // UI will automatically redraw with new FEN
+                        if let Ok(mut game_state) = self.game_state.lock() {
+                            game_state.fen = fen;
+                        }
                     }
                 }
             }
@@ -543,3 +546,350 @@ impl eframe::App for ChessApp {
         ctx.request_repaint();
     }
 }
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn test_default_game_state() {
+        let game_state = GameState::default();
+        assert_eq!(
+            game_state.fen,
+            "rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"
+        );
+        assert_eq!(game_state.player_color, None);
+        assert_eq!(game_state.opponent_name, None);
+        assert_eq!(game_state.match_id, None);
+        assert_eq!(game_state.game_over, None);
+    }
+
+    #[test]
+    fn test_fen_to_board_starting_position() {
+        let app = ChessApp::default();
+        let board = app.fen_to_board("rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR");
+
+        // Test black pieces on rank 0
+        assert_eq!(board[0][0], 'r');
+        assert_eq!(board[0][1], 'n');
+        assert_eq!(board[0][2], 'b');
+        assert_eq!(board[0][3], 'q');
+        assert_eq!(board[0][4], 'k');
+        assert_eq!(board[0][5], 'b');
+        assert_eq!(board[0][6], 'n');
+        assert_eq!(board[0][7], 'r');
+
+        // Test black pawns on rank 1
+        for col in 0..8 {
+            assert_eq!(board[1][col], 'p');
+        }
+
+        // Test empty squares in the middle
+        for row in 2..6 {
+            for col in 0..8 {
+                assert_eq!(board[row][col], ' ');
+            }
+        }
+
+        // Test white pawns on rank 6
+        for col in 0..8 {
+            assert_eq!(board[6][col], 'P');
+        }
+
+        // Test white pieces on rank 7
+        assert_eq!(board[7][0], 'R');
+        assert_eq!(board[7][1], 'N');
+        assert_eq!(board[7][2], 'B');
+        assert_eq!(board[7][3], 'Q');
+        assert_eq!(board[7][4], 'K');
+        assert_eq!(board[7][5], 'B');
+        assert_eq!(board[7][6], 'N');
+        assert_eq!(board[7][7], 'R');
+    }
+
+    #[test]
+    fn test_fen_to_board_with_numbers() {
+        let app = ChessApp::default();
+        let board = app.fen_to_board("4k3/8/8/8/8/8/8/4K3");
+
+        // Test empty squares around kings
+        for row in 0..8 {
+            for col in 0..8 {
+                if (row == 0 && col == 4) || (row == 7 && col == 4) {
+                    continue; // Skip king positions
+                }
+                assert_eq!(board[row][col], ' ');
+            }
+        }
+
+        // Test king positions
+        assert_eq!(board[0][4], 'k'); // black king
+        assert_eq!(board[7][4], 'K'); // white king
+    }
+
+    #[test]
+    fn test_chess_char_to_piece() {
+        let app = ChessApp::default();
+
+        // Test white pieces
+        assert_eq!(app.chess_char_to_piece('K'), "♔");
+        assert_eq!(app.chess_char_to_piece('Q'), "♕");
+        assert_eq!(app.chess_char_to_piece('R'), "♖");
+        assert_eq!(app.chess_char_to_piece('B'), "♗");
+        assert_eq!(app.chess_char_to_piece('N'), "♘");
+        assert_eq!(app.chess_char_to_piece('P'), "♙");
+
+        // Test black pieces
+        assert_eq!(app.chess_char_to_piece('k'), "♚");
+        assert_eq!(app.chess_char_to_piece('q'), "♛");
+        assert_eq!(app.chess_char_to_piece('r'), "♜");
+        assert_eq!(app.chess_char_to_piece('b'), "♝");
+        assert_eq!(app.chess_char_to_piece('n'), "♞");
+        assert_eq!(app.chess_char_to_piece('p'), "♟︎");
+
+        // Test invalid piece
+        assert_eq!(app.chess_char_to_piece('X'), "");
+        assert_eq!(app.chess_char_to_piece(' '), "");
+    }
+
+    #[test]
+    fn test_chess_app_default() {
+        let app = ChessApp::default();
+
+        assert_eq!(app.server_port, "9001");
+        assert_eq!(app.username, "Player");
+        assert!(app.tx_to_network.is_none());
+        assert!(app.rx_from_network.is_none());
+        assert!(app.selected_square.is_none());
+
+        // Verify initial state is MainMenu
+        match app.state {
+            AppState::MainMenu => (),
+            _ => panic!("Expected initial state to be MainMenu"),
+        }
+    }
+
+    #[test]
+    fn test_game_state_clone() {
+        let mut original = GameState::default();
+        original.player_color = Some("white".to_string());
+        original.opponent_name = Some("Opponent".to_string());
+        original.match_id = Some(Uuid::new_v4());
+        original.game_over = Some("Checkmate".to_string());
+
+        let cloned = original.clone();
+
+        assert_eq!(original.fen, cloned.fen);
+        assert_eq!(original.player_color, cloned.player_color);
+        assert_eq!(original.opponent_name, cloned.opponent_name);
+        assert_eq!(original.match_id, cloned.match_id);
+        assert_eq!(original.game_over, cloned.game_over);
+    }
+
+    #[test]
+    fn test_handle_click_selection() {
+        let mut app = ChessApp::default();
+
+        // Initially no square should be selected
+        assert_eq!(app.selected_square, None);
+
+        // Click on a square should select it
+        app.handle_click(3, 4);
+        assert_eq!(app.selected_square, Some((3, 4)));
+
+        // Click on another square should deselect and send move (if tx exists)
+        // Since we don't have a real tx in tests, we just verify the selection is cleared
+        app.handle_click(4, 4);
+        assert_eq!(app.selected_square, None);
+    }
+
+    #[test]
+    fn test_process_network_messages_match_found() {
+        let mut app = ChessApp::default();
+        let (tx, mut rx) = mpsc::unbounded_channel();
+        app.rx_from_network = Some(rx);
+
+        // Send a MatchFound message
+        let match_id = Uuid::new_v4();
+        let message = ServerMessage2::MatchFound {
+            match_id,
+            color: "white".to_string(),
+            opponent_name: "TestOpponent".to_string(),
+        };
+
+        tx.send(message).unwrap();
+
+        // Process the message
+        app.process_network_messages();
+
+        // State should transition to InGame
+        match app.state {
+            AppState::InGame => (),
+            _ => panic!("Expected state to transition to InGame"),
+        }
+    }
+
+    #[test]
+    fn test_process_network_messages_game_over() {
+        let mut app = ChessApp::default();
+        let (tx, mut rx) = mpsc::unbounded_channel();
+        app.rx_from_network = Some(rx);
+
+        // Send a GameEnd message
+        let message = ServerMessage2::GameEnd {
+            winner: "White won by checkmate".to_string(),
+        };
+
+        tx.send(message).unwrap();
+
+        // Process the message
+        app.process_network_messages();
+
+        // State should transition to GameOver
+        match app.state {
+            AppState::GameOver => (),
+            _ => panic!("Expected state to transition to GameOver"),
+        }
+    }
+
+    #[test]
+    fn test_process_network_messages_ui_update() {
+        let mut app = ChessApp::default();
+        let (tx, mut rx) = mpsc::unbounded_channel();
+        app.rx_from_network = Some(rx);
+
+        // Send a UIUpdate message
+        let new_fen = "rnbqkbnr/pppppppp/8/8/4P3/8/PPPP1PPP/RNBQKBNR b KQkq e3 0 1".to_string();
+        let message = ServerMessage2::UIUpdate {
+            fen: new_fen.clone(),
+        };
+
+        tx.send(message).unwrap();
+
+        // Process the message
+        app.process_network_messages();
+
+        // Game state should be updated with new FEN
+        let game_state = app.game_state.lock().unwrap();
+        assert_eq!(game_state.fen, new_fen);
+    }
+
+    #[test]
+    fn test_process_network_messages_ok_response() {
+        let mut app = ChessApp::default();
+        app.state = AppState::Connecting;
+        let (tx, mut rx) = mpsc::unbounded_channel();
+        app.rx_from_network = Some(rx);
+
+        // Send an Ok message
+        let message = ServerMessage2::Ok { response: Ok(()) };
+
+        tx.send(message).unwrap();
+
+        // Process the message
+        app.process_network_messages();
+
+        // State should transition to FindingMatch when in Connecting state
+        match app.state {
+            AppState::FindingMatch => (),
+            _ => panic!("Expected state to transition to FindingMatch"),
+        }
+    }
+
+    #[test]
+    fn test_fen_edge_cases() {
+        let app = ChessApp::default();
+
+        // Test empty board
+        let empty_board = app.fen_to_board("8/8/8/8/8/8/8/8");
+        for row in 0..8 {
+            for col in 0..8 {
+                assert_eq!(empty_board[row][col], ' ');
+            }
+        }
+
+        // Test FEN with multiple digit numbers
+        let board = app.fen_to_board("k7/8/8/8/8/8/8/7K");
+        assert_eq!(board[0][0], 'k');
+        assert_eq!(board[7][7], 'K');
+
+        // Test FEN with mixed pieces and numbers
+        let board = app.fen_to_board("r3k2r/8/8/8/8/8/8/R3K2R");
+        assert_eq!(board[0][0], 'r');
+        assert_eq!(board[0][4], 'k');
+        assert_eq!(board[0][7], 'r');
+        assert_eq!(board[7][0], 'R');
+        assert_eq!(board[7][4], 'K');
+        assert_eq!(board[7][7], 'R');
+    }
+
+    #[tokio::test]
+    async fn test_client_event_serialization() {
+        // Test Join event
+        let join_event = ClientEvent::Join {
+            username: "test".to_string(),
+        };
+        let serialized = serde_json::to_string(&join_event).unwrap();
+        assert!(serialized.contains("Join"));
+        assert!(serialized.contains("test"));
+
+        // Test FindMatch event
+        let find_match_event = ClientEvent::FindMatch;
+        let serialized = serde_json::to_string(&find_match_event).unwrap();
+        assert!(serialized.contains("FindMatch"));
+
+        // Test Move event
+        let chess_move = ChessMove::Quiet {
+            piece_type: engine::piecetype::PieceType::WhiteKing,
+            from_square: BoardSquare { x: 0, y: 1 },
+            to_square: BoardSquare { x: 2, y: 2 },
+            promotion_piece: None,
+        };
+        let move_event = ClientEvent::Move { step: chess_move };
+        let serialized = serde_json::to_string(&move_event).unwrap();
+        assert!(serialized.contains("Move"));
+
+        // Test Resign event
+        let resign_event = ClientEvent::Resign;
+        let serialized = serde_json::to_string(&resign_event).unwrap();
+        assert!(serialized.contains("Resign"));
+    }
+
+    #[test]
+    fn test_server_message_deserialization() {
+        // Test Ok message
+        let ok_json = r#"{"Ok":{"response":{"Ok":null}}}"#;
+        let message: ServerMessage2 = serde_json::from_str(ok_json).unwrap();
+        match message {
+            ServerMessage2::Ok { response } => {
+                assert!(response.is_ok());
+            }
+            _ => panic!("Expected Ok message"),
+        }
+
+        // Test MatchFound message
+        let match_found_json = r#"{"MatchFound":{"match_id":"12345678-1234-1234-1234-123456789012","color":"white","opponent_name":"Test"}}"#;
+        let message: ServerMessage2 = serde_json::from_str(match_found_json).unwrap();
+        match message {
+            ServerMessage2::MatchFound {
+                match_id,
+                color,
+                opponent_name,
+            } => {
+                assert_eq!(color, "white");
+                assert_eq!(opponent_name, "Test");
+            }
+            _ => panic!("Expected MatchFound message"),
+        }
+
+        // Test UIUpdate message
+        let ui_update_json =
+            r#"{"UIUpdate":{"fen":"rnbqkbnr/pppppppp/8/8/8/8/PPPPPPPP/RNBQKBNR w KQkq - 0 1"}}"#;
+        let message: ServerMessage2 = serde_json::from_str(ui_update_json).unwrap();
+        match message {
+            ServerMessage2::UIUpdate { fen } => {
+                assert!(fen.contains("rnbqkbnr"));
+            }
+            _ => panic!("Expected UIUpdate message"),
+        }
+    }
+}