def METHOD_NAME(self, testdata):
    """
    Tests using traces instead of stream objects as input parameters.
    """
    st1 = read(testdata['ref_STS2'])
    st2 = read(testdata['ref_unknown'])
    calfile = testdata['STS2_simp.cal']
    # stream
    freq, amp, phase = rel_calib_stack(st1, st2, calfile, 20, smooth=10,
                                       save_data=False)
    # traces
    freq2, amp2, phase2 = rel_calib_stack(st1[0], st2[0], calfile, 20,
                                          smooth=10, save_data=False)
    np.testing.assert_array_almost_equal(freq, freq2, decimal=4)
    np.testing.assert_array_almost_equal(amp, amp2, decimal=4)
    np.testing.assert_array_almost_equal(phase, phase2, decimal=4)