modules/analysis/common/src/test/org/apache/lucene/analysis/ngram/NGramTokenFilterTest.java

package org.apache.lucene.analysis.ngram;

/**
 * Licensed to the Apache Software Foundation (ASF) under one or more
 * contributor license agreements.  See the NOTICE file distributed with
 * this work for additional information regarding copyright ownership.
 * The ASF 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.
 */

import org.apache.lucene.analysis.Analyzer;
import org.apache.lucene.analysis.MockTokenizer;
import org.apache.lucene.analysis.TokenFilter;
import org.apache.lucene.analysis.TokenStream;
import org.apache.lucene.analysis.BaseTokenStreamTestCase;
import org.apache.lucene.analysis.Tokenizer;
import org.apache.lucene.analysis.core.KeywordTokenizer;
import org.apache.lucene.analysis.core.WhitespaceTokenizer;
import org.apache.lucene.analysis.miscellaneous.ASCIIFoldingFilter;

import java.io.Reader;
import java.io.StringReader;

/**
 * Tests {@link NGramTokenFilter} for correctness.
 */
public class NGramTokenFilterTest extends BaseTokenStreamTestCase {
  private TokenStream input;
  
  @Override
  public void setUp() throws Exception {
    super.setUp();
    input = new MockTokenizer(new StringReader("abcde"), MockTokenizer.WHITESPACE, false);
  }
  
  public void testInvalidInput() throws Exception {
    boolean gotException = false;
    try {        
      new NGramTokenFilter(input, 2, 1);
    } catch (IllegalArgumentException e) {
      gotException = true;
    }
    assertTrue(gotException);
  }
  
  public void testInvalidInput2() throws Exception {
    boolean gotException = false;
    try {        
      new NGramTokenFilter(input, 0, 1);
    } catch (IllegalArgumentException e) {
      gotException = true;
    }
    assertTrue(gotException);
  }
  
  public void testUnigrams() throws Exception {
    NGramTokenFilter filter = new NGramTokenFilter(input, 1, 1);
    assertTokenStreamContents(filter, new String[]{"a","b","c","d","e"}, new int[]{0,1,2,3,4}, new int[]{1,2,3,4,5});
  }
  
  public void testBigrams() throws Exception {
    NGramTokenFilter filter = new NGramTokenFilter(input, 2, 2);
    assertTokenStreamContents(filter, new String[]{"ab","bc","cd","de"}, new int[]{0,1,2,3}, new int[]{2,3,4,5});
  }
  
  public void testNgrams() throws Exception {
    NGramTokenFilter filter = new NGramTokenFilter(input, 1, 3);
    assertTokenStreamContents(filter,
        new String[]{"a","b","c","d","e", "ab","bc","cd","de", "abc","bcd","cde"}, 
        new int[]{0,1,2,3,4, 0,1,2,3, 0,1,2},
        new int[]{1,2,3,4,5, 2,3,4,5, 3,4,5}
        );
  }
  
  public void testOversizedNgrams() throws Exception {
    NGramTokenFilter filter = new NGramTokenFilter(input, 6, 7);
    assertTokenStreamContents(filter, new String[0], new int[0], new int[0]);
  }
  
  public void testSmallTokenInStream() throws Exception {
    input = new MockTokenizer(new StringReader("abc de fgh"), MockTokenizer.WHITESPACE, false);
    NGramTokenFilter filter = new NGramTokenFilter(input, 3, 3);
    assertTokenStreamContents(filter, new String[]{"abc","fgh"}, new int[]{0,7}, new int[]{3,10});
  }
  
  public void testReset() throws Exception {
    WhitespaceTokenizer tokenizer = new WhitespaceTokenizer(TEST_VERSION_CURRENT, new StringReader("abcde"));
    NGramTokenFilter filter = new NGramTokenFilter(tokenizer, 1, 1);
    assertTokenStreamContents(filter, new String[]{"a","b","c","d","e"}, new int[]{0,1,2,3,4}, new int[]{1,2,3,4,5});
    tokenizer.reset(new StringReader("abcde"));
    assertTokenStreamContents(filter, new String[]{"a","b","c","d","e"}, new int[]{0,1,2,3,4}, new int[]{1,2,3,4,5});
  }
  
  // LUCENE-3642
  // EdgeNgram blindly adds term length to offset, but this can take things out of bounds
  // wrt original text if a previous filter increases the length of the word (in this case æ -> ae)
  // so in this case we behave like WDF, and preserve any modified offsets
  public void testInvalidOffsets() throws Exception {
    Analyzer analyzer = new Analyzer() {
      @Override
      protected TokenStreamComponents createComponents(String fieldName, Reader reader) {
        Tokenizer tokenizer = new MockTokenizer(reader, MockTokenizer.WHITESPACE, false);
        TokenFilter filters = new ASCIIFoldingFilter(tokenizer);
        filters = new NGramTokenFilter(filters, 2, 2);
        return new TokenStreamComponents(tokenizer, filters);
      }
    };
    assertAnalyzesTo(analyzer, "mosfellsbær",
        new String[] { "mo", "os", "sf", "fe", "el", "ll", "ls", "sb", "ba", "ae", "er" },
        new int[]    {    0,    0,    0,    0,    0,    0,    0,    0,    0,    0,    0 },
        new int[]    {   11,   11,   11,   11,   11,   11,   11,   11,   11,   11,   11 });
  }
  
  /** blast some random strings through the analyzer */
  public void testRandomStrings() throws Exception {
    Analyzer a = new Analyzer() {
      @Override
      protected TokenStreamComponents createComponents(String fieldName, Reader reader) {
        Tokenizer tokenizer = new MockTokenizer(reader, MockTokenizer.WHITESPACE, false);
        return new TokenStreamComponents(tokenizer, 
            new NGramTokenFilter(tokenizer, 2, 15));
      }    
    };
    checkRandomData(random, a, 10000*RANDOM_MULTIPLIER);
  }
  
  public void testEmptyTerm() throws Exception {
    Analyzer a = new Analyzer() {
      @Override
      protected TokenStreamComponents createComponents(String fieldName, Reader reader) {
        Tokenizer tokenizer = new KeywordTokenizer(reader);
        return new TokenStreamComponents(tokenizer, 
            new NGramTokenFilter(tokenizer, 2, 15));
      }    
    };
    checkAnalysisConsistency(random, a, random.nextBoolean(), "");
  }
}