def METHOD_NAME(self, cosmo_cls, ba):
    """Test initialization for values of ``w0``."""
    # test that it works with units
    ba.arguments["w0"] = ba.arguments["w0"] << u.one  # ensure units
    cosmo = cosmo_cls(*ba.args, **ba.kwargs)
    assert cosmo.w0 == ba.arguments["w0"]
    # also without units
    ba.arguments["w0"] = ba.arguments["w0"].value  # strip units
    cosmo = cosmo_cls(*ba.args, **ba.kwargs)
    assert cosmo.w0 == ba.arguments["w0"]
    # must be dimensionless
    ba.arguments["w0"] = 10 * u.km
    with pytest.raises(TypeError):
        cosmo_cls(*ba.args, **ba.kwargs)