text: # BSD 3-Clause License; see https://github.com/scikit-hep/uproot4/blob/main/LICENSE
  
  
  import multiprocessing
  import sys
  
  import pytest
  import skhep_testdata
  
  import uproot
  
  
  def test_empty():
      with uproot.open(skhep_testdata.data_path("uproot-empty.root")) as f:
          t = f["tree"]
          assert t["x"].array(library="np").tolist() == []
          assert t["y"].array(library="np").tolist() == []
          assert t["z"].array(library="np").tolist() == []
  
  
  def readone(filename):
      with uproot.open(filename) as f:
          f.decompression_executor = uproot.ThreadPoolExecutor()
          t = f["events"]
          b = t["px1"]
          b.array(library="np")
  
  
  def test_multiprocessing():
      with multiprocessing.Pool(1) as pool:
          out = pool.map(
              readone,
              [
                  skhep_testdata.data_path("uproot-Zmumu.root"),
                  skhep_testdata.data_path("uproot-Zmumu-zlib.root"),
              ],
          )
          list(out)
  