### Question:
FileSystemDatasetReader extends AbstractDatasetReader<E> { @Override public String toString() { return Objects.toStringHelper(this) .add("fileSystem", fileSystem) .add("path", path) .add("schema", schema) .add("state", state) .add("reader", reader) .toString(); } FileSystemDatasetReader(FileSystem fileSystem, Path path, Schema schema,
      Class<E> type); @Override void initialize(); @Override boolean hasNext(); @Override E next(); @Override void close(); @Override boolean isOpen(); @Override String toString();  }### Answer:
@Test public void testEvolvedSchema() throws IOException { Schema schema = SchemaBuilder.record("mystring").fields() .requiredString("text") .name("text2").type().stringType().stringDefault("N/A") .endRecord(); FileSystemDatasetReader<Record> reader = new FileSystemDatasetReader<Record>( fileSystem, new Path(Resources.getResource("data/strings-100.avro") .getFile()), schema, Record.class); checkReaderBehavior(reader, 100, new RecordValidator<Record>() { @Override public void validate(Record record, int recordNum) { Assert.assertEquals(String.valueOf(recordNum), record.get("text").toString()); Assert.assertEquals("N/A", record.get("text2").toString()); } }); }