Reported in https://github.com/google/guava/issues/3086#issuecomment-378523615

Needs a fix like https://github.com/google/guava/commit/8f22dbc8ea0c1abdf044846057f6df8201ee9961
* Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */
package com.google.common.io;
import static com.google.common.truth.Truth.assertThat;
import com.google.common.collect.Iterables;
import com.google.common.jimfs.Configuration;
import com.google.common.jimfs.Jimfs;
import com.google.errorprone.annotations.CanIgnoreReturnValue;
import java.io.IOException;
import java.nio.file.Files;
import java.nio.file.Path;
import junit.framework.TestCase;
/**
 * Tests for {@link MoreFiles#fileTraverser()}.
 *
 * @author Jens Nyman
 */
public class MoreFilesFileTraverserTest extends TestCase {
  private Path rootDir;
  @Override
  public void setUp() throws IOException {
    rootDir = Jimfs.newFileSystem(Configuration.unix()).getPath("/tmp");
    Files.createDirectory(rootDir);
  }
  @Override
  public void tearDown() throws IOException {