def test_periodic_left(gfdl_datadir):
ds = xr.open_dataset(os.path.join(gfdl_datadir, 'test_gfdl.nc'), decode_times=False)
dom = GCMDataset(ds)
ptemp = dom.make_periodic_left(ds.temp)
assert len(ptemp.coords['lon']) == 129
assert np.all(ptemp.isel(lon=0) == ptemp.isel(lon=-1))
