def test_zero_siso(self): """Evaluate the zeros of a SISO system.""" # extract only first input / first output system of sys222. This system is denoted sys111 # or tf111 tf111 = ss2tf(self.sys222) sys111 = tf2ss(tf111[0, 0]) # compute zeros as root of the characteristic polynomial at the numerator of tf111 # this method is simple and assumed as valid in this test true_z = np.sort(tf111[0, 0].zero()) # Compute the zeros through ab08nd, which is tested here z = np.sort(sys111.zero()) np.testing.assert_almost_equal(true_z, z)