def test_axis_tilt():
    apparent_zenith = pd.Series([30])
    apparent_azimuth = pd.Series([135])

    tracker_data = tracking.singleaxis(apparent_zenith, apparent_azimuth,
                                       axis_tilt=30, axis_azimuth=180,
                                       max_angle=90, backtrack=True, 
                                       gcr=2.0/7.0)
    
    expect = pd.DataFrame({'aoi': 7.286245, 'surface_azimuth': 142.65730,
                           'surface_tilt': 35.98741, 'tracker_theta': -20.88121},
                           index=[0], dtype=np.float64)
    
    assert_frame_equal(expect, tracker_data)
    
    tracker_data = tracking.singleaxis(apparent_zenith, apparent_azimuth,
                                       axis_tilt=30, axis_azimuth=0,
                                       max_angle=90, backtrack=True, 
                                       gcr=2.0/7.0)
    
    expect = pd.DataFrame({'aoi': 47.6632, 'surface_azimuth': 50.96969,
                           'surface_tilt': 42.5152, 'tracker_theta': 31.6655},
                           index=[0], dtype=np.float64)
    
    assert_frame_equal(expect, tracker_data)
dataset/ETHPy150Open pvlib/pvlib-python/pvlib/test/test_tracking.py/test_axis_tilt/original