@Test
public void testEmptyFileIsOnlyFileAndNotZeroIndex() throws IOException {

  fileSystem.createNewFile(new Path(shardPath.getParent(), "data-001.json"));
  checkNextKeyValueWouldBlock();
  fileSystem.createNewFile(new Path(shardPath.getParent(), "data-002.json"));
  // Second file-marker with different index causes IllegalStateException.
  assertThrows(IllegalStateException.class, () -> recordReader.nextKeyValue());
}