Improve test

Author: smalyshev

x-pack/plugin/esql/src/internalClusterTest/java/org/elasticsearch/xpack/esql/action/AbstractCrossClusterTestCase.java

@@ -146,12 +146,21 @@ protected static void assertClusterMetadataInResponse(EsqlQueryResponse resp, bo
             } else {
                 final Object partial = esqlResponseAsMap.get("is_partial");
                 if (partial != null && (Boolean) partial) {
-                    // If we have partial response, we could have cluster metadata, it should contain details
+                    // If we have partial response, we could have cluster metadata, it should contain details.
+                    // Details should not be empty, and it should contain clusters with failures.
                     if (clusters != null) {
                         @SuppressWarnings("unchecked")
                         Map<String, Object> inner = (Map<String, Object>) clusters;
                         assertThat(inner, aMapWithSize(1));
                         assertTrue(inner.containsKey("details"));
+                        @SuppressWarnings("unchecked")
+                        Map<String, Object> details = (Map<String, Object>) inner.get("details");
+                        assertThat(details.size(), greaterThanOrEqualTo(1));
+                        details.forEach((k, v) -> {
+                            @SuppressWarnings("unchecked")
+                            Map<String, Object> cluster = (Map<String, Object>) v;
+                            assertTrue(cluster.containsKey("failures"));
+                        });
                     }
                 } else {
                     assertNull(clusters);