package org.apache.lucene.search.grouping;

/*
 * 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.document.Field;
import org.apache.lucene.document.FieldType;
import org.apache.lucene.search.Sort;
import org.apache.lucene.search.SortField;
import org.apache.lucene.util.BytesRef;
import org.apache.lucene.util.LuceneTestCase;
import org.apache.lucene.util._TestUtil;

import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.Random;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.fail;

/**
 * Base class for grouping related tests.
 */
// TODO (MvG) : The grouping tests contain a lot of code duplication. Try to move the common code to this class..
public class AbstractGroupingTestCase extends LuceneTestCase {
  
  protected String generateRandomNonEmptyString() {
    String randomValue;
    do {
      // B/c of DV based impl we can't see the difference between an empty string and a null value.
      // For that reason we don't generate empty string groups.
      randomValue = _TestUtil.randomRealisticUnicodeString(random);
    } while ("".equals(randomValue));
    return randomValue;
  }

}

package org.apache.lucene.search.grouping;

/*
 * 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.document.Field;
import org.apache.lucene.document.FieldType;
import org.apache.lucene.search.Sort;
import org.apache.lucene.search.SortField;
import org.apache.lucene.util.BytesRef;
import org.apache.lucene.util.LuceneTestCase;
import org.apache.lucene.util._TestUtil;
import org.junit.Ignore;

import java.util.ArrayList;
import java.util.Comparator;
import java.util.List;
import java.util.Random;

import static org.junit.Assert.assertEquals;
import static org.junit.Assert.fail;

/**
 * Base class for grouping related tests.
 */
// TODO (MvG) : The grouping tests contain a lot of code duplication. Try to move the common code to this class..
@Ignore("Maven Surefire will attempt to run this test suite without an @Ignore annotation.")
public class AbstractGroupingTestCase extends LuceneTestCase {
  
  protected String generateRandomNonEmptyString() {
    String randomValue;
    do {
      // B/c of DV based impl we can't see the difference between an empty string and a null value.
      // For that reason we don't generate empty string groups.
      randomValue = _TestUtil.randomRealisticUnicodeString(random);
    } while ("".equals(randomValue));
    return randomValue;
  }

}

Add @Ignore annotation to AbstractGroupingTestCase to allow Maven Surefire to succeed (otherwise, Maven fails with error "No runnable methods!")