code: ///////////////////////////////////////////////////////////////////////////////////////////////
  // checkstyle: Checks Java source code and other text files for adherence to a set of rules.
  // Copyright (C) 2001-2023 the original author or authors.
  //
  // This library is free software; you can redistribute it and/or
  // modify it under the terms of the GNU Lesser General Public
  // License as published by the Free Software Foundation; either
  // version 2.1 of the License, or (at your option) any later version.
  //
  // This library is distributed in the hope that it will be useful,
  // but WITHOUT ANY WARRANTY; without even the implied warranty of
  // MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  // Lesser General Public License for more details.
  //
  // You should have received a copy of the GNU Lesser General Public
  // License along with this library; if not, write to the Free Software
  // Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA
  ///////////////////////////////////////////////////////////////////////////////////////////////
  
  package com.puppycrawl.tools.checkstyle;
  
  import static com.google.common.truth.Truth.assertWithMessage;
  import static com.puppycrawl.tools.checkstyle.internal.utils.TestUtil.isUtilsClassHasPrivateConstructor;
  
  import java.util.HashMap;
  import java.util.Map;
  
  import javax.xml.parsers.ParserConfigurationException;
  
  import org.junit.jupiter.api.Test;
  import org.xml.sax.SAXException;
  import org.xml.sax.XMLReader;
  
  import com.puppycrawl.tools.checkstyle.internal.utils.TestUtil;
  
  public class XmlLoaderTest {
  
      @Test
      public void testParserConfiguredSuccessfully() throws Exception {
          final DummyLoader dummyLoader = new DummyLoader(new HashMap<>(1));
          final XMLReader parser = TestUtil.getInternalState(dummyLoader, "parser");
          assertWithMessage("Invalid entity resolver")
              .that(parser.getEntityResolver())
              .isEqualTo(dummyLoader);
      }
  
      @Test
      public void testIsProperUtilsClass() throws ReflectiveOperationException {
          assertWithMessage("Constructor is not private")
                  .that(isUtilsClassHasPrivateConstructor(
                          XmlLoader.LoadExternalDtdFeatureProvider.class))
                  .isTrue();
      }
  
      @Test
      public void testResolveEntityDefault() throws Exception {
          final Map<String, String> map = new HashMap<>();
          map.put("predefined", "/google.xml");
          final DummyLoader dummyLoader = new DummyLoader(map);
          assertWithMessage("Invalid entity")
              .that(dummyLoader.resolveEntity("notPredefined", "BAD"))
              .isNull();
      }
  
      @Test
      public void testResolveEntityMap() throws Exception {
          final Map<String, String> map = new HashMap<>();
          map.put("predefined", "/google.xml");
          final DummyLoader dummyLoader = new DummyLoader(map);
          assertWithMessage("Invalid entity")
              .that(dummyLoader.resolveEntity("predefined", "BAD"))
              .isNotNull();
      }
  
      private static final class DummyLoader extends XmlLoader {
  
          private DummyLoader(Map<String, String> publicIdToResourceNameMap)
                  throws SAXException, ParserConfigurationException {
              super(publicIdToResourceNameMap);
          }
  
      }
  
  }
  