bugfix: the problem test case (#3349)

server/src/test/java/io/seata/server/coordinator/DefaultCoordinatorMetricsTest.java

@@ -19,6 +19,9 @@ import java.io.IOException;
 import java.util.HashMap;
 import java.util.Map;
 
+import org.junit.jupiter.api.Assertions;
+import org.junit.jupiter.api.Test;
+
 import io.seata.core.exception.TransactionException;
 import io.seata.core.protocol.transaction.GlobalBeginRequest;
 import io.seata.core.protocol.transaction.GlobalBeginResponse;
@@ -30,8 +33,9 @@ import io.seata.core.rpc.RpcContext;
 import io.seata.metrics.Measurement;
 import io.seata.server.metrics.MetricsManager;
 import io.seata.server.session.SessionHolder;
-import org.junit.jupiter.api.Assertions;
-import org.junit.jupiter.api.Test;
+
+
+import static io.seata.server.coordinator.DefaultCoordinatorTest.MockServerMessageSender;
 
 /**
  * Test Metrics
@@ -42,7 +46,7 @@ public class DefaultCoordinatorMetricsTest {
     @Test
     public void test() throws IOException, TransactionException, InterruptedException {
         SessionHolder.init(null);
-        DefaultCoordinator coordinator = new DefaultCoordinator(null);
+        DefaultCoordinator coordinator = new DefaultCoordinator(new MockServerMessageSender());
         coordinator.init();
         try {
             MetricsManager.get().init();