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 java.util.Map;
  import java.util.TreeMap;
  
  import org.junit.jupiter.api.Test;
  
  import com.puppycrawl.tools.checkstyle.api.CheckstyleException;
  
  public class DefaultConfigurationTest {
  
      @Test
      public void testGetPropertyNames() {
          final DefaultConfiguration config = new DefaultConfiguration("MyConfig");
          config.addProperty("property", "value");
          final String[] actual = config.getPropertyNames();
          final String[] expected = {"property"};
          assertWithMessage("Invalid property names")
              .that(actual)
              .isEqualTo(expected);
      }
  
      @Test
      public void testAddPropertyAndGetProperty() throws CheckstyleException {
          final DefaultConfiguration config = new DefaultConfiguration("MyConfig");
          config.addProperty("property", "first");
          assertWithMessage("Invalid property value")
              .that(config.getProperty("property"))
              .isEqualTo("first");
          config.addProperty("property", "second");
          assertWithMessage("Invalid property value")
              .that(config.getProperty("property"))
              .isEqualTo("first,second");
      }
  
      /*
       * This method is deprecated due to usage of deprecated DefaultConfiguration#addAttribute
       * we keep this method until https://github.com/checkstyle/checkstyle/issues/11722
       */
      @Deprecated(since = "10.2")
      @Test
      public void testDeprecatedAttributeMethods() throws CheckstyleException {
          final DefaultConfiguration config = new DefaultConfiguration("MyConfig");
          config.addAttribute("attribute", "first");
          final String[] actual = config.getAttributeNames();
          final String[] expected = {"attribute"};
          assertWithMessage("Invalid attribute names")
              .that(actual)
              .isEqualTo(expected);
          assertWithMessage("Invalid property value")
              .that(config.getAttribute("attribute"))
              .isEqualTo("first");
          config.addAttribute("attribute", "second");
          assertWithMessage("Invalid property value")
              .that(config.getAttribute("attribute"))
              .isEqualTo("first,second");
      }
  
      @Test
      public void testGetName() {
          final DefaultConfiguration config = new DefaultConfiguration("MyConfig");
          assertWithMessage("Invalid configuration name")
              .that(config.getName())
              .isEqualTo("MyConfig");
      }
  
      @Test
      public void testRemoveChild() {
          final DefaultConfiguration config = new DefaultConfiguration("MyConfig");
          final DefaultConfiguration configChild = new DefaultConfiguration("childConfig");
          assertWithMessage("Invalid children count")
              .that(config.getChildren().length)
              .isEqualTo(0);
          config.addChild(configChild);
          assertWithMessage("Invalid children count")
              .that(config.getChildren().length)
              .isEqualTo(1);
          config.removeChild(configChild);
          assertWithMessage("Invalid children count")
              .that(config.getChildren().length)
              .isEqualTo(0);
      }
  
      @Test
      public void testAddMessageAndGetMessages() {
          final DefaultConfiguration config = new DefaultConfiguration("MyConfig");
          config.addMessage("key", "value");
          final Map<String, String> expected = new TreeMap<>();
          expected.put("key", "value");
          assertWithMessage("Invalid message map")
              .that(config.getMessages())
              .isEqualTo(expected);
      }
  
      @Test
      public void testExceptionForNonExistentProperty() {
          final String name = "MyConfig";
          final DefaultConfiguration config = new DefaultConfiguration(name);
          final String propertyName = "NonExistent#$%";
          try {
              config.getProperty(propertyName);
              assertWithMessage("Exception is expected").fail();
          }
          catch (CheckstyleException expected) {
              assertWithMessage("Invalid exception message")
                  .that(expected.getMessage())
                  .isEqualTo("missing key '" + propertyName + "' in " + name);
          }
      }
  
      @Test
      public void testDefaultMultiThreadConfiguration() {
          final String name = "MyConfig";
          final DefaultConfiguration config = new DefaultConfiguration(name);
          final ThreadModeSettings singleThreadMode =
                  ThreadModeSettings.SINGLE_THREAD_MODE_INSTANCE;
          assertWithMessage("Invalid thread mode")
              .that(config.getThreadModeSettings())
              .isEqualTo(singleThreadMode);
      }
  
      @Test
      public void testMultiThreadConfiguration() {
          final String name = "MyConfig";
          final ThreadModeSettings multiThreadMode =
                  new ThreadModeSettings(4, 2);
          final DefaultConfiguration config = new DefaultConfiguration(name, multiThreadMode);
          assertWithMessage("Invalid thread mode")
              .that(config.getThreadModeSettings())
              .isEqualTo(multiThreadMode);
      }
  
  }
  