src/test/java/ch/unibas/dmi/dbis/cs108/casono/client/network/TestServer.java

@@ -0,0 +1,89 @@
+package ch.unibas.dmi.dbis.cs108.casono.client.network;
+
+import ch.unibas.dmi.dbis.cs108.casono.server.network.transport.RawPacket;
+import ch.unibas.dmi.dbis.cs108.casono.server.network.transport.TcpTransport;
+import java.io.DataOutputStream;
+import java.io.IOException;
+import java.net.ServerSocket;
+import java.net.Socket;
+import java.nio.charset.StandardCharsets;
+import java.util.Map;
+import java.util.concurrent.ConcurrentHashMap;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+import java.util.concurrent.atomic.AtomicInteger;
+
+/**
+ * Minimal test server that speaks the RawPacket/TcpTransport protocol used by
+ * ClientService. Provides deterministic responses for CREATE_LOBBY and
+ * GET_LOBBY_STATUS so unit tests can run without a real backend.
+ */
+public class TestServer implements AutoCloseable {
+    private final ServerSocket serverSocket;
+    private final ExecutorService exec = Executors.newSingleThreadExecutor();
+    private final AtomicInteger nextLobbyId = new AtomicInteger(1);
+    private final Map<Integer, String> lobbyStatus = new ConcurrentHashMap<>();
+    private volatile boolean running = true;
+
+    public TestServer() throws IOException {
+        this.serverSocket = new ServerSocket(0);
+        exec.submit(this::acceptLoop);
+    }
+
+    public int getPort() {
+        return serverSocket.getLocalPort();
+    }
+
+    private void acceptLoop() {
+        try (Socket client = serverSocket.accept()) {
+            TcpTransport transport = new TcpTransport(client);
+            while (running) {
+                RawPacket request = transport.read();
+                String payload = request.payload();
+                String response = handleRequest(payload);
+                // send the response payload followed by +OK
+                transport.write(new RawPacket(request.requestId(), response));
+                transport.write(new RawPacket(request.requestId(), "+OK"));
+            }
+        } catch (IOException e) {
+            if (running) {
+                throw new RuntimeException(e);
+            }
+        }
+    }
+
+    private String handleRequest(String payload) {
+        if (payload == null)
+            return "";
+        if (payload.startsWith("CREATE_LOBBY")) {
+            int id = nextLobbyId.getAndIncrement();
+            lobbyStatus.put(id, "created");
+            return Integer.toString(id);
+        }
+        if (payload.startsWith("GET_LOBBY_STATUS")) {
+            // payload format: GET_LOBBY_STATUS ID=<id>
+            String[] parts = payload.split("ID=");
+            if (parts.length == 2) {
+                try {
+                    int id = Integer.parseInt(parts[1].trim());
+                    return lobbyStatus.getOrDefault(id, "created");
+                } catch (NumberFormatException e) {
+                    return "created";
+                }
+            }
+            return "created";
+        }
+        if (payload.startsWith("JOIN_LOBBY")) {
+            // no-op
+            return "";
+        }
+        return "";
+    }
+
+    @Override
+    public void close() throws Exception {
+        running = false;
+        serverSocket.close();
+        exec.shutdownNow();
+    }
+}

src/test/java/ch/unibas/dmi/dbis/cs108/casono/client/ui/lobbyui/LobbyButtonGridManagerTest.java

@@ -3,19 +3,32 @@ package ch.unibas.dmi.dbis.cs108.casono.client.ui.lobbyui;
 import static org.junit.jupiter.api.Assertions.*;
 
 import javafx.scene.layout.GridPane;
+import ch.unibas.dmi.dbis.cs108.casono.client.network.ClientService;
 import org.junit.jupiter.api.*;
 
 class LobbyButtonGridManagerTest {
     LobbyButtonGridManager gridManager;
     LobbyButtonTranslationManager translationManager;
     GridPane gridPane;
+    ch.unibas.dmi.dbis.cs108.casono.client.network.TestServer testServer;
 
     @BeforeEach
-    void setUp() {
+    void setUp() throws Exception {
         gridPane = new GridPane();
         translationManager = LobbyButtonTranslationManager.getInstance();
         translationManager.getButtonIdToLobbyId().clear();
-        gridManager = new LobbyButtonGridManager(gridPane, translationManager);
+        // Start an in-process test server and connect a real ClientService to it.
+        testServer = new ch.unibas.dmi.dbis.cs108.casono.client.network.TestServer();
+        String host = "127.0.0.1";
+        int port = testServer.getPort();
+        ClientService clientService = new ClientService(host, port);
+        gridManager = new LobbyButtonGridManager(gridPane, translationManager, clientService);
+    }
+
+    @AfterEach
+    void tearDown() throws Exception {
+        if (testServer != null)
+            testServer.close();
     }
 
     @Test