Method AssertCannotConsume

cpp/src/arrow/dataset/scanner_test.cc:2059–2065

  }

  void AssertCannotConsume() {
    if (!next.is_valid()) {
      next = generator();
    }
    SleepABit();
    ASSERT_FALSE(next.is_finished());
  }

  void AssertFinished() {
    if (!next.is_valid()) {