def METHOD_NAME(self):
    l = "bar"
    self.pg.createlayer(l)
    self.pg.layers[l][0][0] = 100
    self.pg.decaycellvalues(l, 3)
    self.assertEqual(int(round(self.pg.layers[l][0][0])), 79)
    self.pg.decaycellvalues(l, 3)
    self.assertEqual(int(round(self.pg.layers[l][0][0])), 63)
    self.pg.decaycellvalues(l, 3)
    self.assertEqual(int(round(self.pg.layers[l][0][0])), 50)
    self.pg.decaycellvalues(l, 3, 50)
    self.assertEqual(int(round(self.pg.layers[l][0][0])), 50)