Tweaks for Mockito on Java 21

Author: acogoluegnes

pom.xml

@@ -399,7 +399,9 @@
           <excludes>
             <exclude>**/*TestSuite.java</exclude>
           </excludes>
+          <argLine>-XX:+EnableDynamicAgentLoading</argLine>
           <systemPropertyVariables>
+            <net.bytebuddy.experimental>true</net.bytebuddy.experimental>
             <rabbitmqctl.bin>DOCKER:rabbitmq</rabbitmqctl.bin>
           </systemPropertyVariables>
         </configuration>

src/test/java/com/rabbitmq/stream/impl/ConsumersCoordinatorTest.java

@@ -164,8 +164,10 @@ public Client.ClientParameters shutdownListener(
 
   @AfterEach
   void tearDown() throws Exception {
-    // just taking the opportunity to check toString() generates valid JSON
-    MonitoringTestUtils.extract(coordinator);
+    if (coordinator != null) {
+      // just taking the opportunity to check toString() generates valid JSON
+      MonitoringTestUtils.extract(coordinator);
+    }
     if (scheduledExecutorService != null) {
       scheduledExecutorService.shutdownNow();
     }