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    * 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
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  package org.apache.commons.csv.issues;
  
  import static org.junit.jupiter.api.Assertions.assertEquals;
  import static org.junit.jupiter.api.Assertions.assertFalse;
  import static org.junit.jupiter.api.Assertions.assertThrows;
  import static org.junit.jupiter.api.Assertions.assertTrue;
  
  import java.io.Reader;
  import java.io.StringReader;
  import java.util.Arrays;
  import java.util.Iterator;
  
  import org.apache.commons.csv.CSVFormat;
  import org.apache.commons.csv.CSVParser;
  import org.apache.commons.csv.CSVRecord;
  import org.junit.jupiter.api.Test;
  
  public class JiraCsv247Test {
  
      @Test
      public void testHeadersMissingOneColumnWhenAllowingMissingColumnNames() throws Exception {
          final CSVFormat format = CSVFormat.DEFAULT.builder().setHeader().setAllowMissingColumnNames(true).build();
  
          assertTrue(format.getAllowMissingColumnNames(), "We should allow missing column names");
  
          final Reader in = new StringReader("a,,c,d,e\n1,2,3,4,5\nv,w,x,y,z");
          try (final CSVParser parser = format.parse(in)) {
              assertEquals(Arrays.asList("a", "", "c", "d", "e"), parser.getHeaderNames());
              final Iterator<CSVRecord> iterator = parser.iterator();
              CSVRecord record = iterator.next();
              assertEquals("1", record.get(0));
              assertEquals("2", record.get(1));
              assertEquals("3", record.get(2));
              assertEquals("4", record.get(3));
              assertEquals("5", record.get(4));
              record = iterator.next();
              assertEquals("v", record.get(0));
              assertEquals("w", record.get(1));
              assertEquals("x", record.get(2));
              assertEquals("y", record.get(3));
              assertEquals("z", record.get(4));
              assertFalse(iterator.hasNext());
          }
      }
  
      @Test
      public void testHeadersMissingThrowsWhenNotAllowingMissingColumnNames() {
          final CSVFormat format = CSVFormat.DEFAULT.builder().setHeader().build();
  
          assertFalse(format.getAllowMissingColumnNames(), "By default we should not allow missing column names");
  
          assertThrows(IllegalArgumentException.class, () -> {
              try (final Reader reader = new StringReader("a,,c,d,e\n1,2,3,4,5\nv,w,x,y,z");
                  CSVParser parser = format.parse(reader);) {
                  // should fail
              }
          }, "1 missing column header is not allowed");
  
          assertThrows(IllegalArgumentException.class, () -> {
              try (final Reader reader = new StringReader("a,,c,d,\n1,2,3,4,5\nv,w,x,y,z");
                  CSVParser parser = format.parse(reader);) {
                  // should fail
              }
          }, "2+ missing column headers is not allowed!");
      }
  }