Fix MetadataMappingServiceTests.testClusterStateIsNotChangedWithIdenticalMappings (#82408)

This would pass even though the mapping JSON was broken (as was the request without an index
set on it for that matter) because it didn't check the CS update result for exceptions.

server/src/test/java/org/elasticsearch/cluster/metadata/MetadataMappingServiceTests.java

@@ -9,7 +9,6 @@
 package org.elasticsearch.cluster.metadata;
 
 import org.elasticsearch.action.admin.indices.mapping.put.PutMappingClusterStateUpdateRequest;
-import org.elasticsearch.cluster.ClusterState;
 import org.elasticsearch.cluster.ClusterStateTaskExecutor;
 import org.elasticsearch.cluster.service.ClusterService;
 import org.elasticsearch.common.compress.CompressedXContent;
@@ -57,22 +56,25 @@ public class MetadataMappingServiceTests extends ESSingleNodeTestCase {
     }
 
     public void testClusterStateIsNotChangedWithIdenticalMappings() throws Exception {
-        createIndex("test", client().admin().indices().prepareCreate("test"));
+        final IndexService indexService = createIndex("test", client().admin().indices().prepareCreate("test"));
 
         final MetadataMappingService mappingService = getInstanceFromNode(MetadataMappingService.class);
         final ClusterService clusterService = getInstanceFromNode(ClusterService.class);
         final PutMappingClusterStateUpdateRequest request = new PutMappingClusterStateUpdateRequest("""
-            { "properties" { "field": { "type": "text" }}}""");
-        ClusterState result = mappingService.putMappingExecutor.execute(
+            { "properties": { "field": { "type": "text" }}}""").indices(new Index[] { indexService.index() });
+        ClusterStateTaskExecutor.ClusterTasksResult<?> result = mappingService.putMappingExecutor.execute(
             clusterService.state(),
             Collections.singletonList(request)
-        ).resultingState;
-
-        assertFalse(result != clusterService.state());
+        );
+        assertTrue(result.executionResults.values().stream().noneMatch(res -> res.isSuccess() == false));
 
-        ClusterState result2 = mappingService.putMappingExecutor.execute(result, Collections.singletonList(request)).resultingState;
+        ClusterStateTaskExecutor.ClusterTasksResult<?> result2 = mappingService.putMappingExecutor.execute(
+            result.resultingState,
+            Collections.singletonList(request)
+        );
+        assertTrue(result.executionResults.values().stream().noneMatch(res -> res.isSuccess() == false));
 
-        assertSame(result, result2);
+        assertSame(result2.resultingState, result.resultingState);
     }
 
     public void testMappingVersion() throws Exception {