text: import pandas as pd
  import numpy as np
  import load_data
  import Z_direction
  
  def test_Z_direction():
      z_direction, Z_dir = Z_direction.Z_direction("PHASEdata.csv","up")
      try:
          Z_direction.Z_direction(123,"up") or Z_direction.Z_direction("PHASEdata.csv",123)
      except(Exception):
          pass
      else:
          raise Exception("Input error. String-string expected")
          
      assert len(Z_dir)==500, 'z error'
     
      return