assertTrue(SessionSetupHandler.class.isAssignableFrom(impl.getClass()), "Type should be assignable");
    }

    @Test
    @DisplayName("Edge: null is not an instance of the interface")
    void testNullIsNotInstance() {
        // Assert
        assertFalse(SessionSetupHandler.class.isInstance(null));
    }

    @Test

     */
    public OptionalEntity<StopwordsFile> getStopwordsFile(final String dictId) {
        return dictionaryManager.getDictionaryFile(dictId)
                .filter(StopwordsFile.class::isInstance)
                .map(file -> OptionalEntity.of((StopwordsFile) file))
                .orElse(OptionalEntity.empty());
    }

    /**
     * Retrieves a specific stopword item by its ID.
     *

     */
    public OptionalEntity<SynonymFile> getSynonymFile(final String dictId) {
        return dictionaryManager.getDictionaryFile(dictId)
                .filter(SynonymFile.class::isInstance)
                .map(file -> OptionalEntity.of((SynonymFile) file))
                .orElse(OptionalEntity.empty());
    }

    /**
     * Retrieves a specific synonym item by its ID.
     *

@GwtCompatible
final class Platform {
  static boolean isInstanceOfThrowableClass(
      @Nullable Throwable t, Class<? extends Throwable> expectedClass) {
    return expectedClass.isInstance(t);
  }

  static void restoreInterruptIfIsInterruptedException(Throwable t) {
    checkNotNull(t); // to satisfy NullPointerTester
    if (t instanceof InterruptedException) {
      currentThread().interrupt();

   *
   * <p><b>Discouraged:</b> Prefer using {@code clazz::isInstance} or {@code x -> x instanceof
   * Clazz}, but note that lambdas do not have human-readable {@link #toString()} representations
   * and are not serializable.
   */
  @GwtIncompatible // Class.isInstance
  public static <T extends @Nullable Object> Predicate<T> instanceOf(Class<?> clazz) {

     */
    public OptionalEntity<KuromojiFile> getKuromojiFile(final String dictId) {
        return dictionaryManager.getDictionaryFile(dictId)
                .filter(KuromojiFile.class::isInstance)
                .map(file -> OptionalEntity.of((KuromojiFile) file))
                .orElse(OptionalEntity.empty());
    }

    /**
     * Get a Kuromoji item.
     *
     * @param dictId The dictionary ID.

     */
    public OptionalEntity<ProtwordsFile> getProtwordsFile(final String dictId) {
        return dictionaryManager.getDictionaryFile(dictId)
                .filter(ProtwordsFile.class::isInstance)
                .map(file -> OptionalEntity.of((ProtwordsFile) file))
                .orElse(OptionalEntity.empty());
    }

    /**
     * Gets a specific protected words item by ID.

   * This does perform a little more work than necessary, so another option is to insert an
   * unchecked cast at some later point:
   *
   * {@snippet :
   * @SuppressWarnings("unchecked") // safe because of ::isInstance check
   * ImmutableList<NewType> result =
   *     (ImmutableList) stream.filter(NewType.class::isInstance).collect(toImmutableList());
   * }
   */

   * This does perform a little more work than necessary, so another option is to insert an
   * unchecked cast at some later point:
   *
   * {@snippet :
   * @SuppressWarnings("unchecked") // safe because of ::isInstance check
   * ImmutableList<NewType> result =
   *     (ImmutableList) stream.filter(NewType.class::isInstance).collect(toImmutableList());
   * }
   */

        // Arrange: create an implementation instance
        SmbRenewableCredentials impl = supplier.get();

        // Act: call renew
        CredentialsInternal renewed = impl.renew();

        // Assert: verify behavior based on scenario
        if (expectSame) {
            assertSame(impl, renewed, "renew() should return the same instance");
        } else if (expectNew) {