def testGetButterworthLpf(self): time = range(500) fundamental = 8*arctan(1)/30 noise = 8*arctan(1)/4 input = time[:] for t in time: input[t]=cos(fundamental*t) + cos(noise*t) output = DigitalFilter.get_butterworth_lpf(input, 20) self.assertEqual(len(input), len(output), 'good length') self.assertAlmostEqual(output[499], -0.89911731,msg='good Butterworth')