return actionClass;
    }

    /**
     * Overrides fillInStackTrace to return null for performance optimization.
     * This prevents stack trace generation for this exception type.
     *
     * @return null to skip stack trace generation
     */
    @Override
    public synchronized Throwable fillInStackTrace() {
        return null;
    }

    }

    @Test
    public void test_fillInStackTrace() {
        // Test fillInStackTrace returns null for performance optimization
        UserRoleLoginException exception = new UserRoleLoginException(RootAction.class);
        Throwable result = exception.fillInStackTrace();
        assertNull(result);

        // Verify that stack trace is not generated

    @Test
    public void test_fillInStackTrace() {
        // Test fillInStackTrace method
        UnsupportedSearchException exception = new UnsupportedSearchException("Stack trace test");

        StackTraceElement[] originalStackTrace = exception.getStackTrace();
        assertNotNull(originalStackTrace);

        Throwable filled = exception.fillInStackTrace();
        assertSame(exception, filled);

        assertTrue(foundTestMethod);
    }

    @Test
    public void test_fillInStackTrace() {
        // Test that fillInStackTrace works properly
        JobNotFoundException exception = new JobNotFoundException("Fill stack trace test");

        Throwable filled = exception.fillInStackTrace();

        assertNotNull(filled);
        assertEquals(exception, filled);
        assertNotNull(filled.getStackTrace());

        assertNull(localizedMessage);
    }

    @Test
    public void test_fillInStackTrace() {
        // Test fillInStackTrace method
        DictionaryExpiredException exception = new DictionaryExpiredException();
        Throwable result = exception.fillInStackTrace();

        assertNotNull(result);
        assertSame(exception, result);

        StackTraceElement[] stackTrace = result.getStackTrace();

    }

    @Test
    public void test_fillInStackTrace() {
        // Test fillInStackTrace method
        ResultOffsetExceededException exception = new ResultOffsetExceededException("Stack trace test");

        StackTraceElement[] originalStackTrace = exception.getStackTrace();
        Throwable result = exception.fillInStackTrace();
        StackTraceElement[] newStackTrace = exception.getStackTrace();

        assertTrue(toString.contains(message));
    }

    @Test
    public void test_fillInStackTrace() {
        // Test fillInStackTrace method
        DataStoreException exception = new DataStoreException("Stack trace test");
        Throwable filled = exception.fillInStackTrace();

        assertNotNull(filled);
        assertEquals(exception, filled);
        assertNotNull(filled.getStackTrace());

      // IteratorTester doesn't expect exceptions for hasNext().
      return true;
    }

    @Override
    public E next() {
      ex.fillInStackTrace();
      throw ex;
    }

    @Override
    public void remove() {
      ex.fillInStackTrace();
      throw ex;
    }
  }

      // IteratorTester doesn't expect exceptions for hasNext().
      return true;
    }

    @Override
    public E next() {
      ex.fillInStackTrace();
      throw ex;
    }

    @Override
    public void remove() {
      ex.fillInStackTrace();
      throw ex;
    }
  }

    static final Failure FALLBACK_INSTANCE =
        new Failure(
            new Throwable("Failure occurred while trying to finish a future.") {
              @Override
              public Throwable fillInStackTrace() {
                return this; // no stack trace
              }
            });
    final Throwable exception;

    Failure(Throwable exception) {
      this.exception = checkNotNull(exception);