Fixed Integration Tests

Given that the Server instance is a class instance, it's used by all the tests in the class and if the tests run in parallel then some asserts could fail if we are considering that the connected clients of the server are only the clients that the current test connected.
To avoid this we should always query the Server.ActiveClients property (and not the Server.ActiveConnections) and filtering by the client ids connected in the test.

src/IntegrationTests/ConnectionSpec.cs

@@ -88,12 +88,15 @@ public async Task when_clients_connect_and_disconnect_then_server_raises_events(
 		public async Task when_connect_clients_and_one_client_drops_connection_then_other_client_survives()
 		{
 			var fooClient = await GetClientAsync();
+			var fooClientId = GetClientId();
 			var barClient = await GetClientAsync();
+			var barClientId = GetClientId();
 
-			await fooClient.ConnectAsync(new MqttClientCredentials(GetClientId()));
-			await barClient.ConnectAsync(new MqttClientCredentials(GetClientId()));
+			await fooClient.ConnectAsync(new MqttClientCredentials(fooClientId));
+			await barClient.ConnectAsync(new MqttClientCredentials(barClientId));
 
-			var initialConnectedClients = server.ActiveClients.Count();
+			var clientIds = new List<string> { fooClientId, barClientId };
+			var initialConnectedClients = server.ActiveClients.Where(c => clientIds.Contains(c)).Count();
 			var exceptionThrown = false;
 
 			try
@@ -110,18 +113,19 @@ public async Task when_connect_clients_and_one_client_drops_connection_then_othe
 
 			while (!serverSignal.IsSet)
 			{
-				if (server.ActiveConnections == 1 && server.ActiveClients.Count() == 1)
+				if (!server.ActiveClients.Any(c => c == fooClientId))
 				{
 					serverSignal.Set();
 				}
 			}
 
 			serverSignal.Wait();
 
+			var finalConnectedClients = server.ActiveClients.Where(c => clientIds.Contains(c)).Count();
+
 			Assert.Equal(2, initialConnectedClients);
 			Assert.True(exceptionThrown);
-			Assert.Equal(1, server.ActiveConnections);
-			Assert.Equal(1, server.ActiveClients.Count());
+			Assert.Equal(1, finalConnectedClients);
 
 			fooClient.Dispose();
 			barClient.Dispose();
@@ -167,8 +171,7 @@ public async Task when_connecting_twice_with_same_client_with_disconnecting_then
 			await client.DisconnectAsync();
 			await client.ConnectAsync(new MqttClientCredentials(clientId));
 
-			Assert.Equal(1, server.ActiveConnections);
-			Assert.Equal(1, server.ActiveClients.Count());
+			Assert.Equal(1, server.ActiveClients.Count(c => c == clientId));
 
 			client.Dispose();
 		}