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 * Licensed to Elasticsearch under one or more contributor
 * license agreements. See the NOTICE file distributed with
 * this work for additional information regarding copyright
 * ownership. Elasticsearch licenses this file to you under
 * the Apache License, Version 2.0 (the "License"); you may
 * not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing,
 * software distributed under the License is distributed on an
 * "AS IS" BASIS, WITHOUT WARRANTIES OR CONDITIONS OF ANY
 * KIND, either express or implied.  See the License for the
 * specific language governing permissions and limitations
 * under the License.
 */

package org.elasticsearch.index.engine.internal;

import org.elasticsearch.action.admin.indices.segments.IndexSegments;
import org.elasticsearch.action.admin.indices.segments.IndexShardSegments;
import org.elasticsearch.action.admin.indices.segments.IndicesSegmentResponse;
import org.elasticsearch.action.admin.indices.segments.ShardSegments;
import org.elasticsearch.common.settings.ImmutableSettings;
import org.elasticsearch.index.engine.Segment;
import org.elasticsearch.test.ElasticsearchIntegrationTest;
import org.hamcrest.Matchers;
import org.junit.Test;

import java.util.Collection;
import java.util.HashSet;
import java.util.Set;

public class InternalEngineIntegrationTest extends ElasticsearchIntegrationTest {

    @Test
    public void testSetIndexCompoundOnFlush() {
        client().admin().indices().prepareCreate("test").setSettings(ImmutableSettings.builder().put("number_of_replicas", 0).put("number_of_shards", 1)).get();
        ensureGreen();
        client().prepareIndex("test", "foo").setSource("field", "foo").get();
        refresh();
        assertTotalCompoundSegments(1, 1, "test");
        client().admin().indices().prepareUpdateSettings("test")
                .setSettings(ImmutableSettings.builder().put(InternalEngine.INDEX_COMPOUND_ON_FLUSH, false)).get();
        client().prepareIndex("test", "foo").setSource("field", "foo").get();
        refresh();
        assertTotalCompoundSegments(1, 2, "test");

        client().admin().indices().prepareUpdateSettings("test")
                .setSettings(ImmutableSettings.builder().put(InternalEngine.INDEX_COMPOUND_ON_FLUSH, true)).get();
        client().prepareIndex("test", "foo").setSource("field", "foo").get();
        refresh();
        assertTotalCompoundSegments(2, 3, "test");
    }

    private void assertTotalCompoundSegments(int i, int t, String index) {
        IndicesSegmentResponse indicesSegmentResponse = client().admin().indices().prepareSegments(index).get();
        IndexSegments indexSegments = indicesSegmentResponse.getIndices().get(index);
        assertNotNull(indexSegments);
        assertNotNull(indexSegments.getShards());
        Collection<IndexShardSegments> values = indexSegments.getShards().values();
        int compounds = 0;
        int total = 0;
        for (IndexShardSegments indexShardSegments : values) {
            for (ShardSegments s : indexShardSegments) {
                for (Segment segment : s) {
                    if (segment.isSearch() && segment.getNumDocs() > 0) {
                        if (segment.isCompound()) {
                            compounds++;
                        }
                        total++;
                    }
                }
            }
        }
        assertThat(compounds, Matchers.equalTo(i));
        assertThat(total, Matchers.equalTo(t));
    }

    private Set<Segment> segments(IndexSegments segments) {
        Set<Segment> segmentSet = new HashSet<>();
        for (IndexShardSegments s : segments) {
            for (ShardSegments shardSegments : s) {
                segmentSet.addAll(shardSegments.getSegments());
            }
        }
        return segmentSet;
    }
}

@@ -2744,32 +2744,144 @@
 s(index).get();%0A
+        assertNotNull(%22indices segments response should contain indices%22, indicesSegmentResponse.getIndices());%0A
         IndexSeg

Add an assert for null indices in InternalEngineIntegrationTest