'Test adding new cards and updating existing cards from an iterable of
cards and card tuples.'

def test_update_from_iterable(self):

    header = fits.Header([('A', 'B'), ('C', 'D')])
    header.update([('A', 'E'), fits.Card('F', 'G')])
    assert (header['A'] == 'E')
    assert (header[0] == 'E')
    assert ('F' in header)
    assert (header['F'] == 'G')
    assert (header[(-1)] == 'G')
