register test feature for sparse vector

Author: markjhoy

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/XPackFeatures.java

@@ -12,6 +12,8 @@
 
 import java.util.Set;
 
+import static org.elasticsearch.index.mapper.vectors.SparseVectorFieldMapper.SPARSE_VECTOR_INDEX_OPTIONS_FEATURE;
+
 /**
  * Provides the XPack features that this version of the code supports
  */
@@ -20,4 +22,9 @@ public class XPackFeatures implements FeatureSpecification {
     public Set<NodeFeature> getFeatures() {
         return Set.of();
     }
+
+    @Override
+    public Set<NodeFeature> getTestFeatures() {
+        return Set.of(SPARSE_VECTOR_INDEX_OPTIONS_FEATURE);
+    }
 }