TestPrefixStringMatcher.java

/**
 * 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.
 */

package org.apache.nutch.util;

import org.junit.Assert;
import org.junit.Test;

/** Unit tests for PrefixStringMatcher. */
public class TestPrefixStringMatcher {

  private final static int NUM_TEST_ROUNDS = 20;
  private final static int MAX_TEST_PREFIXES = 100;
  private final static int MAX_PREFIX_LEN = 10;
  private final static int NUM_TEST_INPUTS_PER_ROUND = 100;
  private final static int MAX_INPUT_LEN = 20;

  private final static char[] alphabet = new char[] { 'a', 'b', 'c', 'd',
  // 'e', 'f', 'g', 'h', 'i', 'j',
  // 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r', 's', 't',
  // 'u', 'v', 'w', 'x', 'y', 'z', '1', '2', '3', '4',
  // '5', '6', '7', '8', '9', '0'
  };

  private String makeRandString(int minLen, int maxLen) {
    int len = minLen + (int) (Math.random() * (maxLen - minLen));
    char[] chars = new char[len];

    for (int pos = 0; pos < len; pos++) {
      chars[pos] = alphabet[(int) (Math.random() * alphabet.length)];
    }

    return new String(chars);
  }

  @Test
  public void testPrefixMatcher() {
    int numMatches = 0;
    int numInputsTested = 0;

    for (int round = 0; round < NUM_TEST_ROUNDS; round++) {

      // build list of prefixes
      int numPrefixes = (int) (Math.random() * MAX_TEST_PREFIXES);
      String[] prefixes = new String[numPrefixes];
      for (int i = 0; i < numPrefixes; i++) {
        prefixes[i] = makeRandString(0, MAX_PREFIX_LEN);
      }

      PrefixStringMatcher prematcher = new PrefixStringMatcher(prefixes);

      // test random strings for prefix matches
      for (int i = 0; i < NUM_TEST_INPUTS_PER_ROUND; i++) {
        String input = makeRandString(0, MAX_INPUT_LEN);
        boolean matches = false;
        int longestMatch = -1;
        int shortestMatch = -1;

        for (int j = 0; j < prefixes.length; j++) {

          if ((prefixes[j].length() > 0) && input.startsWith(prefixes[j])) {

            matches = true;
            int matchSize = prefixes[j].length();

            if (matchSize > longestMatch)
              longestMatch = matchSize;

            if ((matchSize < shortestMatch) || (shortestMatch == -1))
              shortestMatch = matchSize;
          }

        }

        if (matches)
          numMatches++;

        numInputsTested++;

        Assert.assertTrue("'" + input + "' should " + (matches ? "" : "not ")
            + "match!", matches == prematcher.matches(input));
        if (matches) {
          Assert.assertTrue(shortestMatch == prematcher.shortestMatch(input)
              .length());
          Assert.assertTrue(input.substring(0, shortestMatch).equals(
              prematcher.shortestMatch(input)));

          Assert.assertTrue(longestMatch == prematcher.longestMatch(input)
              .length());
          Assert.assertTrue(input.substring(0, longestMatch).equals(
              prematcher.longestMatch(input)));

        }
      }
    }

    System.out.println("got " + numMatches + " matches out of "
        + numInputsTested + " tests");
  }

}