Add retry to flaky test in ResponseTimeMonitorTest (jenkinsci#10654)

* Add retry to flaky test in ResponseTimeMonitorTest

* Retry with awaitility

* Update test/src/test/java/hudson/node_monitors/ResponseTimeMonitorTest.java

Co-authored-by: Tim Jacomb <21194782+timja@users.noreply.github.com>

---------

Co-authored-by: Tim Jacomb <21194782+timja@users.noreply.github.com>

Author: strangelookingnerd

test/src/test/java/hudson/node_monitors/ResponseTimeMonitorTest.java

@@ -1,5 +1,6 @@
 package hudson.node_monitors;
 
+import static org.awaitility.Awaitility.await;
 import static org.junit.Assert.assertEquals;
 import static org.junit.Assert.assertNotNull;
 import static org.junit.Assert.assertNull;
@@ -11,6 +12,8 @@
 import hudson.slaves.DumbSlave;
 import hudson.slaves.OfflineCause;
 import hudson.slaves.SlaveComputer;
+import java.util.concurrent.ExecutionException;
+import java.util.concurrent.TimeUnit;
 import org.junit.Rule;
 import org.junit.Test;
 import org.jvnet.hudson.test.InboundAgentRule;
@@ -47,8 +50,15 @@ public void skipOfflineAgent() throws Exception {
         j.disconnectSlave(s);
         assertNull(ResponseTimeMonitor.DESCRIPTOR.monitor(c));
 
-        // Now reconnect and make sure we get a non-null response.
-        c.connect(false).get(); // wait until it's connected
+        // Retry to compensate for test being flaky in CI
+        await().atMost(5, TimeUnit.SECONDS)
+            .ignoreException(ExecutionException.class)
+            .until(() -> {
+                // Now reconnect and make sure we get a non-null response.
+                c.connect(false).get(); // wait until it's connected
+                return true;
+            }
+        );
 
         assertNotNull(ResponseTimeMonitor.DESCRIPTOR.monitor(c));
     }