assertThat(source.sizeIfKnown()).isAbsent();

      assertThrows(IOException.class, () -> source.size());
    }
  }

  public void testEqual() throws IOException {
    try (FileSystem fs = Jimfs.newFileSystem(Configuration.unix())) {
      Path fooPath = fs.getPath("foo");
      Path barPath = fs.getPath("bar");