Improved test stability

src/main/java/net/schmizz/sshj/connection/channel/direct/LocalPortForwarder.java

@@ -137,6 +137,15 @@ public class LocalPortForwarder {
         listen(Thread.currentThread());
     }
 
+    /**
+     * Returns whether this listener is running (ie. whether a thread is attached to it).
+     *
+     * @return
+     */
+    public boolean isRunning() {
+        return this.runningThread != null && !serverSocket.isClosed();
+    }
+
     /**
      * Start listening for incoming connections and forward to remote host as a channel and ensure that the thread is registered.
      * This is useful if for instance {@link #close() is called from another thread}

src/test/groovy/com/hierynomus/sshj/connection/channel/direct/LocalPortForwarderSpec.groovy

@@ -19,6 +19,9 @@ import com.hierynomus.sshj.test.SshFixture
 import net.schmizz.sshj.connection.channel.direct.LocalPortForwarder
 import org.junit.Rule
 import spock.lang.Specification
+import spock.util.concurrent.PollingConditions
+
+import java.util.concurrent.CountDownLatch
 
 class LocalPortForwarderSpec extends Specification {
   @Rule
@@ -44,6 +47,9 @@ class LocalPortForwarderSpec extends Specification {
     thread.start()
 
     then:
+    new PollingConditions().eventually {
+      lpf.isRunning()
+    }
     thread.isAlive()
 
     when: