'Tests that a `ColDefs` can be indexed by column name.'

def test_column_lookup_by_name(self):

    a = fits.Column(name='a', format='D')
    b = fits.Column(name='b', format='D')
    cols = fits.ColDefs([a, b])
    assert (cols['a'] == cols[0])
    assert (cols['b'] == cols[1])
