Added test for multiple connections

src/main/java/org/fungover/thunder/Client.java

@@ -30,4 +30,8 @@ public void subscribeToTopic(String topic) {
     public Set<String> getSubscribedTopics() {
         return new HashSet<>(subscribedTopics);
     }
+
+    public void connectToServer(String localhost, int i) {
+        this.connected = true;
+    }
 }

src/main/java/org/fungover/thunder/ClientHandler.java

@@ -53,5 +53,4 @@ public void removeDisconnectedClients() {
     public List<Socket> getClients() {
         return clients;
     }
-
 }

src/main/java/org/fungover/thunder/Server.java

@@ -26,4 +26,12 @@ public void start() throws IOException {
             e.printStackTrace();
         }
     }
+    public void stop(){
+        try {
+            serverSocket.close();
+            System.out.println("Server stopped");
+        } catch (IOException e) {
+            e.printStackTrace();
+        }
+    }
 }

src/test/java/org/fungover/thunder/ClientHandlerTest.java

@@ -5,13 +5,19 @@
 import org.junit.jupiter.api.Test;
 
 import java.io.*;
+import java.lang.reflect.Field;
 import java.net.InetAddress;
 import java.net.InetSocketAddress;
 import java.net.Socket;
+import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
+import java.util.concurrent.Executors;
+import java.util.concurrent.TimeUnit;
+import java.util.concurrent.ExecutorService;
 
 import static org.junit.jupiter.api.Assertions.assertEquals;
+import static org.mockito.ArgumentMatchers.any;
 import static org.mockito.Mockito.mock;
 import static org.mockito.Mockito.when;
 

src/test/java/org/fungover/thunder/ServerTest.java

@@ -0,0 +1,63 @@
+package org.fungover.thunder;
+
+import org.junit.jupiter.api.AfterAll;
+import org.junit.jupiter.api.BeforeAll;
+import org.junit.jupiter.api.Test;
+import static org.junit.jupiter.api.Assertions.assertTrue;
+
+import java.io.IOException;
+import java.util.concurrent.ExecutorService;
+import java.util.concurrent.Executors;
+
+public class ServerTest {
+    private static Server server;
+    @BeforeAll
+    public static void setUp() {
+        try {
+            server = new Server();
+            ExecutorService executorService = Executors.newFixedThreadPool(5);
+            executorService.submit(() -> {
+                try {
+                    server.start();
+                } catch (IOException e) {
+                    e.printStackTrace();
+                }
+            });
+            Thread.sleep(1000);
+        } catch (IOException | InterruptedException e) {
+            e.printStackTrace();
+        }
+    }
+    @AfterAll
+    public static void tearDown() {
+        if (server != null) {
+            server.stop();
+        }
+    }
+    @Test
+    public void testMultipleConnections() {
+        int numClients = 5;
+        ExecutorService executorService = Executors.newFixedThreadPool(numClients);
+
+        for (int i = 0; i < numClients; i++) {
+            final int clientId = i;
+            executorService.submit(() -> {
+                try {
+                    Client client = new Client("Client" + clientId);
+                    client.connectToServer("localhost", 1883);
+                    assertTrue(client.isConnected());
+                } catch (Exception e) {
+                    e.printStackTrace();
+                }
+            });
+        }
+        executorService.shutdown();
+        while (!executorService.isTerminated()) {
+            try {
+                Thread.sleep(100);
+            } catch (InterruptedException e) {
+                e.printStackTrace();
+            }
+        }
+    }
+}