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.checks;
  
  import static com.google.common.truth.Truth.assertWithMessage;
  import static com.puppycrawl.tools.checkstyle.checks.OrderedPropertiesCheck.MSG_IO_EXCEPTION_KEY;
  import static com.puppycrawl.tools.checkstyle.checks.OrderedPropertiesCheck.MSG_KEY;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.nio.file.Files;
  import java.nio.file.NoSuchFileException;
  import java.util.Collections;
  import java.util.SortedSet;
  
  import org.junit.jupiter.api.Test;
  
  import com.puppycrawl.tools.checkstyle.AbstractModuleTestSupport;
  import com.puppycrawl.tools.checkstyle.DefaultConfiguration;
  import com.puppycrawl.tools.checkstyle.api.FileText;
  import com.puppycrawl.tools.checkstyle.api.Violation;
  import com.puppycrawl.tools.checkstyle.utils.CommonUtil;
  
  public class OrderedPropertiesCheckTest extends AbstractModuleTestSupport {
  
      @Override
      protected String getPackageLocation() {
          return "com/puppycrawl/tools/checkstyle/checks/orderedproperties";
      }
  
      /**
       * Tests the ordinal work of a check.
       * Test of sub keys, repeating key pairs in wrong order
       */
      @Test
      public void testDefault() throws Exception {
          final DefaultConfiguration checkConfig = createModuleConfig(OrderedPropertiesCheck.class);
          final String[] expected = {
              "8: " + getCheckMessage(MSG_KEY, "key1", "key2"),
              "11: " + getCheckMessage(MSG_KEY, "B", "key4"),
              "14: " + getCheckMessage(MSG_KEY, "key3", "key5"),
              "17: " + getCheckMessage(MSG_KEY, "key3", "key5"),
          };
          verify(checkConfig, getPath("InputOrderedProperties.properties"), expected);
      }
  
      @Test
      public void testKeysOnly() throws Exception {
          final DefaultConfiguration checkConfig = createModuleConfig(OrderedPropertiesCheck.class);
          final String[] expected = {
              "3: " + getCheckMessage(MSG_KEY, "key1", "key2"),
          };
          verify(checkConfig, getPath("InputOrderedProperties1OrderKey.properties"), expected);
      }
  
      @Test
      public void testEmptyKeys() throws Exception {
          final DefaultConfiguration checkConfig = createModuleConfig(OrderedPropertiesCheck.class);
          final String[] expected = {
              "3: " + getCheckMessage(MSG_KEY, "key11", "key2"),
          };
          verify(checkConfig, getPath("InputOrderedProperties2EmptyValue.properties"), expected);
      }
  
      @Test
      public void testMalformedValue() throws Exception {
          final DefaultConfiguration checkConfig = createModuleConfig(OrderedPropertiesCheck.class);
          final String fileName =
                  getPath("InputOrderedProperties3MalformedValue.properties");
  
          verify(checkConfig, fileName, "1: "
                  + getCheckMessage(MSG_IO_EXCEPTION_KEY, fileName, "Malformed \\uxxxx encoding."));
      }
  
      @Test
      public void testCommentsMultiLine() throws Exception {
          final DefaultConfiguration checkConfig = createModuleConfig(OrderedPropertiesCheck.class);
          final String[] expected = {
              "5: " + getCheckMessage(MSG_KEY, "aKey", "multi.line"),
          };
          verify(checkConfig, getPath("InputOrderedProperties5CommentsMultiLine.properties"),
                  expected);
      }
  
      @Test
      public void testLineNumberRepeatingPreviousKey() throws Exception {
          final DefaultConfiguration checkConfig = createModuleConfig(OrderedPropertiesCheck.class);
          final String[] expected = {
              "3: " + getCheckMessage(MSG_KEY, "a", "b"),
          };
          verify(checkConfig, getPath("InputOrderedProperties6RepeatingPreviousKey.properties"),
                  expected);
      }
  
      @Test
      public void testShouldNotProcessFilesWithWrongFileExtension() throws Exception {
          final DefaultConfiguration checkConfig = createModuleConfig(OrderedPropertiesCheck.class);
          final String[] expected = CommonUtil.EMPTY_STRING_ARRAY;
          verify(checkConfig, getPath("InputOrderedProperties.txt"), expected);
      }
  
      /**
       * Tests IO exception, that can occur during reading of properties file.
       */
      @Test
      public void testIoException() throws Exception {
          final DefaultConfiguration checkConfig = createModuleConfig(OrderedPropertiesCheck.class);
          final OrderedPropertiesCheck check = new OrderedPropertiesCheck();
          check.configure(checkConfig);
          final String fileName =
                  getPath("InputOrderedPropertiesCheckNotExisting.properties");
          final File file = new File(fileName);
          final FileText fileText = new FileText(file, Collections.emptyList());
          final SortedSet<Violation> violations =
                  check.process(file, fileText);
          assertWithMessage("Wrong violations count")
                  .that(violations)
                  .hasSize(1);
          final Violation violation = violations.iterator().next();
          final String retrievedMessage = violations.iterator().next().getKey();
          assertWithMessage("violation key is not valid")
                  .that(retrievedMessage)
                  .isEqualTo("unable.open.cause");
          assertWithMessage("violation is not valid")
                  .that(getCheckMessage(MSG_IO_EXCEPTION_KEY, fileName, getFileNotFoundDetail(file)))
                  .isEqualTo(violation.getViolation());
      }
  
      /**
       * This test validates the PIT mutation of getIndex().
       * Here the for statement for
       * (int index = startLineNo; index < fileText.size(); index++)
       * will change to
       * for (int index = startLineNo; true; index++)
       * By creating a FileText having no lines it makes sure that
       * fileText.size() returning zero size.
       * This will keep the for loop intact.
       */
      @Test
      public void testKeepForLoopIntact() throws Exception {
  
          final DefaultConfiguration checkConfig = createModuleConfig(OrderedPropertiesCheck.class);
          final OrderedPropertiesCheck check = new OrderedPropertiesCheck();
          check.configure(checkConfig);
          final String fileName =
                  getPath("InputOrderedProperties2EmptyValue.properties");
          final File file = new File(fileName);
          final FileText fileText = new FileText(file, Collections.emptyList());
          final SortedSet<Violation> violations = check.process(file, fileText);
  
          assertWithMessage("Wrong violations count")
                  .that(violations)
                  .hasSize(1);
      }
  
      @Test
      public void testFileExtension() {
  
          final OrderedPropertiesCheck check = new OrderedPropertiesCheck();
          assertWithMessage("File extension should be set")
                  .that(".properties")
                  .isEqualTo(check.getFileExtensions()[0]);
      }
  
      /**
       * Method generates NoSuchFileException details. It tries to open a file that does not exist.
       *
       * @param file to be opened
       * @return localized detail message of {@link NoSuchFileException}
       */
      private static String getFileNotFoundDetail(File file) {
          // Create exception to know detail message we should wait in LocalisedMessage
          try (InputStream stream = Files.newInputStream(file.toPath())) {
              throw new IllegalStateException("File " + file.getPath() + " should not exist");
          }
          catch (IOException ex) {
              return ex.getLocalizedMessage();
          }
      }
  }
  