changed cassini tests to follow new format (#173)

def test_instrument_id(driver):

    with patch('ale.base.label_pds3.Pds3Label.instrument_id', new_callable=PropertyMock) as mock_instrument_id:

        mock_instrument_id.return_value = 'ISSNA'

        assert driver.instrument_id == 'CASSINI_ISS_NAC'

        mock_instrument_id.return_value = 'ISSWA'

        assert driver.instrument_id == 'CASSINI_ISS_WAC'

@patch('ale.base.data_naif.NaifSpice.ikid', 123)

def test_focal_epsilon(driver):

    with patch('ale.base.data_naif.NaifSpice.ikid', new_callable=PropertyMock) as mock_ikid:

        mock_ikid.return_value = 123

    assert driver.focal_epsilon == 1

def test_spacecraft_name(driver):

    assert driver.spacecraft_name == 'CASSINI'

@patch('ale.base.data_naif.NaifSpice.ikid', 123)

def test_focal2pixel_samples(driver):

    with patch('ale.base.data_naif.NaifSpice.ikid', new_callable=PropertyMock) as mock_ikid:

        mock_ikid.return_value = 123

    assert driver.focal2pixel_samples == [0,1000,0]

@patch('ale.base.data_naif.NaifSpice.ikid', 123)

def test_focal2pixel_lines(driver):

    with patch('ale.base.data_naif.NaifSpice.ikid', new_callable=PropertyMock) as mock_ikid:

        mock_ikid.return_value = 123

    assert driver.focal2pixel_lines == [0,0,1000]

def testodtk(driver):

    with patch('ale.base.label_pds3.Pds3Label.instrument_id', new_callable=PropertyMock) as mock_instrument_id:

        mock_instrument_id.return_value = 'ISSNA'

        assert driver.odtk == [float('-8e-6'), 0, 0]

        mock_instrument_id.return_value = 'ISSWA'

        assert driver.odtk == [float('-6.2e-5'), 0, 0]

@patch('ale.base.data_naif.NaifSpice.ikid', 123)

def test_detector_center_line(driver):

    with patch('ale.base.data_naif.NaifSpice.ikid', new_callable=PropertyMock) as mock_ikid:

        mock_ikid.return_value = 123

    assert driver.detector_center_line == 1

@patch('ale.base.data_naif.NaifSpice.ikid', 123)

def test_detector_center_sample(driver):

    with patch('ale.base.data_naif.NaifSpice.ikid', new_callable=PropertyMock) as mock_ikid:

        mock_ikid.return_value = 123

        assert driver.detector_center_sample == 1

def test_sensor_model_version(driver):