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 * the Apache License, Version 2.0 (the "License"); you may
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 * You may obtain a copy of the License at
 *
 *    http://www.apache.org/licenses/LICENSE-2.0
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 * Unless required by applicable law or agreed to in writing,
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package org.elasticsearch.index.similarity;

import org.apache.lucene.search.similarities.BM25Similarity;
import org.apache.lucene.search.similarities.ClassicSimilarity;
import org.elasticsearch.common.settings.Settings;
import org.elasticsearch.index.IndexSettings;
import org.elasticsearch.test.ESTestCase;
import org.elasticsearch.test.IndexSettingsModule;

import java.util.Collections;

import static org.hamcrest.Matchers.instanceOf;

public class SimilarityServiceTests extends ESTestCase {
    public void testDefaultSimilarity() {
        Settings settings = Settings.builder().build();
        IndexSettings indexSettings = IndexSettingsModule.newIndexSettings("test", settings);
        SimilarityService service = new SimilarityService(indexSettings, Collections.emptyMap());
        assertThat(service.getDefaultSimilarity(), instanceOf(BM25Similarity.class));
    }

    // Tests #16594
    public void testOverrideBuiltInSimilarity() {
        Settings settings = Settings.builder().put("index.similarity.BM25.type", "classic").build();
        IndexSettings indexSettings = IndexSettingsModule.newIndexSettings("test", settings);
        try {
            new SimilarityService(indexSettings, Collections.emptyMap());
            fail("can't override bm25");
        } catch (IllegalArgumentException ex) {
            assertEquals(ex.getMessage(), "Cannot redefine built-in Similarity [BM25]");
        }
    }

    public void testOverrideDefaultSimilarity() {
        Settings settings = Settings.builder().put("index.similarity.default.type", "classic")
                .build();
        IndexSettings indexSettings = IndexSettingsModule.newIndexSettings("test", settings);
        SimilarityService service = new SimilarityService(indexSettings, Collections.emptyMap());
        assertTrue(service.getDefaultSimilarity() instanceof ClassicSimilarity);
    }
}