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.UniquePropertiesCheck.MSG_IO_EXCEPTION_KEY;
  import static com.puppycrawl.tools.checkstyle.checks.UniquePropertiesCheck.MSG_KEY;
  
  import java.io.File;
  import java.io.IOException;
  import java.io.InputStream;
  import java.lang.reflect.Constructor;
  import java.lang.reflect.Method;
  import java.nio.file.Files;
  import java.nio.file.NoSuchFileException;
  import java.util.ArrayList;
  import java.util.Collections;
  import java.util.HashMap;
  import java.util.List;
  import java.util.Map;
  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 UniquePropertiesCheckTest extends AbstractModuleTestSupport {
  
      @Override
      protected String getPackageLocation() {
          return "com/puppycrawl/tools/checkstyle/checks/uniqueproperties";
      }
  
      /* Additional test for jacoco, since valueOf()
       * is generated by javac and jacoco reports that
       * valueOf() is uncovered.
       */
      @Test
      public void testLineSeparatorOptionValueOf() {
          final LineSeparatorOption option = LineSeparatorOption.valueOf("CR");
          assertWithMessage("Invalid valueOf result")
              .that(option)
              .isEqualTo(LineSeparatorOption.CR);
      }
  
      /**
       * Tests the ordinal work of a check.
       */
      @Test
      public void testDefault() throws Exception {
          final DefaultConfiguration checkConfig = createModuleConfig(UniquePropertiesCheck.class);
          final String[] expected = {
              "3: " + getCheckMessage(MSG_KEY, "general.exception", 2),
              "5: " + getCheckMessage(MSG_KEY, "DefaultLogger.auditStarted", 2),
              "11: " + getCheckMessage(MSG_KEY, "onlineManual", 3),
              "22: " + getCheckMessage(MSG_KEY, "time stamp", 3),
              "28: " + getCheckMessage(MSG_KEY, "Support Link ", 2),
              "34: " + getCheckMessage(MSG_KEY, "failed", 2),
          };
          verify(checkConfig, getPath("InputUniqueProperties.properties"), expected);
      }
  
      /**
       * Tests the {@link UniquePropertiesCheck#getLineNumber(FileText, String)}
       * method return value.
       *
       * @noinspection JavadocReference
       * @noinspectionreason JavadocReference - reference is required to specify method under test
       */
      @Test
      public void testNotFoundKey() throws Exception {
          final List<String> testStrings = new ArrayList<>(3);
          final Method getLineNumber = UniquePropertiesCheck.class.getDeclaredMethod(
              "getLineNumber", FileText.class, String.class);
          assertWithMessage("Get line number method should be present")
              .that(getLineNumber)
              .isNotNull();
          getLineNumber.setAccessible(true);
          testStrings.add("");
          testStrings.add("0 = 0");
          testStrings.add("445");
          final FileText fileText = new FileText(new File("some.properties"), testStrings);
          final Object lineNumber = getLineNumber.invoke(UniquePropertiesCheck.class,
                  fileText, "some key");
          assertWithMessage("Line number should not be null")
              .that(lineNumber)
              .isNotNull();
          assertWithMessage("Invalid line number")
              .that(lineNumber)
              .isEqualTo(1);
      }
  
      @Test
      public void testDuplicatedProperty() throws Exception {
          final DefaultConfiguration checkConfig = createModuleConfig(UniquePropertiesCheck.class);
          final String[] expected = {
              "2: " + getCheckMessage(MSG_KEY, "key", 2),
          };
          verify(checkConfig, getPath("InputUniquePropertiesWithDuplicates.properties"), expected);
      }
  
      @Test
      public void testShouldNotProcessFilesWithWrongFileExtension() throws Exception {
          final DefaultConfiguration checkConfig = createModuleConfig(UniquePropertiesCheck.class);
          final String[] expected = CommonUtil.EMPTY_STRING_ARRAY;
          verify(checkConfig, getPath("InputUniqueProperties.txt"), expected);
      }
  
      /**
       * Tests IO exception, that can occur during reading of properties file.
       */
      @Test
      public void testIoException() throws Exception {
          final DefaultConfiguration checkConfig = createModuleConfig(UniquePropertiesCheck.class);
          final UniquePropertiesCheck check = new UniquePropertiesCheck();
          check.configure(checkConfig);
          final String fileName =
                  getPath("InputUniquePropertiesCheckNotExisting.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 messages count: " + violations.size())
              .that(violations)
              .hasSize(1);
          final Violation violation = violations.iterator().next();
          final String retrievedMessage = violations.iterator().next().getKey();
          assertWithMessage("violation key '" + retrievedMessage + "' is not valid")
              .that(retrievedMessage)
              .isEqualTo("unable.open.cause");
          assertWithMessage("violation '" + violation.getViolation() + "' is not valid")
              .that(getCheckMessage(MSG_IO_EXCEPTION_KEY, fileName, getFileNotFoundDetail(file)))
              .isEqualTo(violation.getViolation());
      }
  
      @Test
      public void testWrongKeyTypeInProperties() throws Exception {
          final Class<?> uniquePropertiesClass = Class
                  .forName("com.puppycrawl.tools.checkstyle.checks."
                      + "UniquePropertiesCheck$UniqueProperties");
          final Constructor<?> constructor = uniquePropertiesClass.getDeclaredConstructor();
          constructor.setAccessible(true);
          final Object uniqueProperties = constructor.newInstance();
          final Method method = uniqueProperties.getClass().getDeclaredMethod("put", Object.class,
                  Object.class);
          final Object result = method.invoke(uniqueProperties, 1, "value");
          final Map<Object, Object> table = new HashMap<>();
          final Object expected = table.put(1, "value");
          assertWithMessage("Invalid result of put method")
              .that(result)
              .isEqualTo(expected);
  
          final Object result2 = method.invoke(uniqueProperties, 1, "value");
          final Object expected2 = table.put(1, "value");
          assertWithMessage("Value should be substituted")
              .that(result2)
              .isEqualTo(expected2);
      }
  
      /**
       * 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();
          }
      }
  
  }
  