text: from floodsystem.plot import plot_water_level_with_fit, plot_water_levels
  from floodsystem.analysis import polyfit
  from floodsystem.stationdata import build_station_list, update_water_levels
  from floodsystem.station import MonitoringStation
  import floodsystem.stationdata as stationdata
  import datetime
  from floodsystem.datafetcher import fetch_measure_levels
  import numpy
  
  import datetime
  import numpy as np
  import floodsystem.flood as flood
  import floodsystem.plot as plot
  import matplotlib.pyplot as plt
  
  def test_plot_water_levels():
  
      stations = build_station_list()
      update_water_levels(stations)
      dates = np.empty(5, dtype=object)
      levels = np.empty(5, dtype=object)
      dt = 10
      for i in range(5):
          dates[i], levels[i] = fetch_measure_levels(
              stations[i].measure_id, dt=datetime.timedelta(days=dt))
  
          plot_water_levels(stations[i], dates[i], levels[i])
  
      assert plt.show() == None
  
  test_plot_water_levels()