Add roundtripping to ReciprocalRank

modules/rank-eval/src/main/java/org/elasticsearch/index/rankeval/PrecisionAtN.java

@@ -189,5 +189,4 @@ public class PrecisionAtN extends RankedListQualityMetric<PrecisionAtN> {
     public final int hashCode() {
         return Objects.hash(getClass(), n);
     }
-
 }

modules/rank-eval/src/main/java/org/elasticsearch/index/rankeval/ReciprocalRank.java

@@ -36,6 +36,7 @@ import java.util.ArrayList;
 import java.util.Collection;
 import java.util.HashSet;
 import java.util.List;
+import java.util.Objects;
 import java.util.Set;
 
 import javax.naming.directory.SearchResult;
@@ -159,10 +160,27 @@ public class ReciprocalRank extends RankedListQualityMetric<ReciprocalRank> {
     @Override
     public XContentBuilder toXContent(XContentBuilder builder, Params params) throws IOException {
         builder.startObject();
-        builder.startObject(NAME);
+        //builder.startObject(NAME);
         builder.field(MAX_RANK_FIELD.getPreferredName(), this.maxAcceptableRank);
-        builder.endObject();
+        //builder.endObject();
         builder.endObject();
         return builder;
     }
+
+    @Override
+    public final boolean equals(Object obj) {
+        if (this == obj) {
+            return true;
+        }
+        if (obj == null || getClass() != obj.getClass()) {
+            return false;
+        }
+        ReciprocalRank other = (ReciprocalRank) obj;
+        return Objects.equals(maxAcceptableRank, other.maxAcceptableRank);
+    }
+    
+    @Override
+    public final int hashCode() {
+        return Objects.hash(getClass(), maxAcceptableRank);
+    }
 }

modules/rank-eval/src/test/java/org/elasticsearch/index/rankeval/ReciprocalRankTests.java

@@ -24,8 +24,8 @@ import org.elasticsearch.index.Index;
 import org.elasticsearch.index.rankeval.PrecisionAtN.Rating;
 import org.elasticsearch.search.SearchShardTarget;
 import org.elasticsearch.search.internal.InternalSearchHit;
-import org.elasticsearch.test.ESTestCase;
 
+import java.io.IOException;
 import java.util.ArrayList;
 import java.util.Collections;
 import java.util.List;
@@ -33,7 +33,7 @@ import java.util.Vector;
 
 import static java.util.Collections.emptyList;
 
-public class ReciprocalRankTests extends ESTestCase {
+public class ReciprocalRankTests extends XContentRoundtripTestCase<ReciprocalRank> {
 
     public void testMaxAcceptableRank() {
         ReciprocalRank reciprocalRank = new ReciprocalRank();
@@ -123,4 +123,12 @@ public class ReciprocalRankTests extends ESTestCase {
         EvalQueryQuality evaluation = reciprocalRank.evaluate(hits, ratedDocs);
         assertEquals(0.0, evaluation.getQualityLevel(), Double.MIN_VALUE);
     }
+
+    public void testXContentRoundtrip() throws IOException {
+        int position = randomIntBetween(0, 1000);
+
+        ReciprocalRank testItem = new ReciprocalRank(position);
+        roundtrip(testItem);
+    }
+
 }