code: import numpy
  from prototype import Changer
  
  
  def test_changer():
      changer = Changer(0.5, 1, 1)
      matrix = numpy.array([[0, 0, 0]])
      changer.change(matrix)
      assert matrix[0, 2] == 0
      changer.change(matrix)
      assert matrix[0, 2] == -1
      changer.change(matrix)
      assert matrix[0, 2] == 0
  
apis: numpy.array