add unit test

Signed-off-by: xuxiong1 <[email protected]>

Author: xuxiong1

server/src/main/java/org/opensearch/index/engine/Engine.java

@@ -947,6 +947,9 @@ public SegmentsStats segmentsStats(boolean includeSegmentFileSizes, boolean incl
         return stats;
     }
 
+    /**
+     * @return Stats for pull-based ingestion.
+     */
     public PollingIngestStats pollingIngestStats() {
         return null;
     }

server/src/main/java/org/opensearch/indices/pollingingest/PollingIngestStats.java

@@ -79,6 +79,9 @@ public int hashCode() {
         return Objects.hash(messageProcessorStats, consumerStats);
     }
 
+    /**
+     * Stats for message processor
+     */
     @ExperimentalApi
     public static class MessageProcessorStats {
         private final long totalProcessedCount;
@@ -105,6 +108,9 @@ public int hashCode() {
         }
     }
 
+    /**
+     * Stats for consumer (poller)
+     */
     @ExperimentalApi
     public static class ConsumerStats {
         private final long totalPolledCount;
@@ -131,6 +137,9 @@ public int hashCode() {
         }
     }
 
+    /**
+     * Builder for {@link PollingIngestStats}
+     */
     @ExperimentalApi
     public static class Builder {
         private long totalProcessedCount;
@@ -155,6 +164,11 @@ public PollingIngestStats build() {
         }
     }
 
+    /**
+     * Returns a new builder for creating a {@link PollingIngestStats} instance.
+     *
+     * @return a new {@code Builder} instance
+     */
     public static Builder builder() {
         return new Builder();
     }

server/src/test/java/org/opensearch/indices/pollingingest/PollingIngestStatsTests.java

@@ -0,0 +1,58 @@
+/*
+ * SPDX-License-Identifier: Apache-2.0
+ *
+ * The OpenSearch Contributors require contributions made to
+ * this file be licensed under the Apache-2.0 license or a
+ * compatible open source license.
+ */
+
+package org.opensearch.indices.pollingingest;
+
+import org.opensearch.common.io.stream.BytesStreamOutput;
+import org.opensearch.core.common.io.stream.StreamInput;
+import org.opensearch.core.xcontent.MediaTypeRegistry;
+import org.opensearch.core.xcontent.ToXContent;
+import org.opensearch.core.xcontent.XContentBuilder;
+import org.opensearch.test.OpenSearchTestCase;
+
+import java.io.IOException;
+
+public class PollingIngestStatsTests extends OpenSearchTestCase {
+
+    public void testToXContent() throws IOException {
+        PollingIngestStats stats = createTestInstance();
+
+        XContentBuilder builder = MediaTypeRegistry.contentBuilder(MediaTypeRegistry.JSON);
+        builder.startObject();
+        stats.toXContent(builder, ToXContent.EMPTY_PARAMS);
+        builder.endObject();
+
+        String expected = "{\"polling_ingest_stats\":{\"message_processor_stats\":{\"total_processed_count\":"
+            + stats.getMessageProcessorStats().getTotalProcessedCount()
+            + "},\"consumer_stats\":{\"total_polled_count\":"
+            + stats.getConsumerStats().getTotalPolledCount()
+            + "}}}";
+
+        assertEquals(expected, builder.toString());
+    }
+
+    public void testSerialization() throws IOException {
+        PollingIngestStats original = createTestInstance();
+
+        try (BytesStreamOutput output = new BytesStreamOutput()) {
+            original.writeTo(output);
+
+            try (StreamInput input = output.bytes().streamInput()) {
+                PollingIngestStats deserialized = new PollingIngestStats(input);
+                assertEquals(original, deserialized);
+            }
+        }
+    }
+
+    private PollingIngestStats createTestInstance() {
+        return PollingIngestStats.builder()
+            .setTotalProcessedCount(randomNonNegativeLong())
+            .setTotalPolledCount(randomNonNegativeLong())
+            .build();
+    }
+}