private Independence parseIndependenceMeasure(String expr) {
  if ("ChiSquared".equals(expr)) {
    return new IndependenceChiSquared();
  } else if ("Standardized".equals(expr)) {
    return new IndependenceStandardized();
  } else if ("Saturated".equals(expr)) {
    return new IndependenceSaturated();
  } else {
    throw new RuntimeException("Invalid independence measure: " + expr);
  }
}
 

/**
 * dfi with no parameters
 */
public void test() throws Exception {
  Similarity sim = getSimilarity("text");
  assertEquals(DFISimilarity.class, sim.getClass());
  DFISimilarity dfi = (DFISimilarity) sim;
  assertTrue(dfi.getDiscountOverlaps());
  assertTrue(dfi.getIndependence() instanceof IndependenceChiSquared);
}
 

@Before
public void setupIndex() throws IOException {
    dirUnderTest = newDirectory();
    List<Similarity> sims = Arrays.asList(
            new ClassicSimilarity(),
            new SweetSpotSimilarity(), // extends Classic
            new BM25Similarity(),
            new LMDirichletSimilarity(),
            new BooleanSimilarity(),
            new LMJelinekMercerSimilarity(0.2F),
            new AxiomaticF3LOG(0.5F, 10),
            new DFISimilarity(new IndependenceChiSquared()),
            new DFRSimilarity(new BasicModelG(), new AfterEffectB(), new NormalizationH1()),
            new IBSimilarity(new DistributionLL(), new LambdaDF(), new NormalizationH3())
        );
    similarity = sims.get(random().nextInt(sims.size()));

    indexWriterUnderTest = new RandomIndexWriter(random(), dirUnderTest, newIndexWriterConfig().setSimilarity(similarity));
    for (int i = 0; i < docs.length; i++) {
        Document doc = new Document();
        doc.add(newStringField("id", "" + i, Field.Store.YES));
        doc.add(newField("field", docs[i], Store.YES));
        indexWriterUnderTest.addDocument(doc);
    }
    indexWriterUnderTest.commit();
    indexWriterUnderTest.forceMerge(1);
    indexWriterUnderTest.flush();


    indexReaderUnderTest = indexWriterUnderTest.getReader();
    searcherUnderTest = newSearcher(indexReaderUnderTest);
    searcherUnderTest.setSimilarity(similarity);
}