def test_concat(self):
self.ds['bar'] = Variable(['x', 'y'], np.random.randn(10, 20))
foo = self.ds['foo'].select()
bar = self.ds['bar'].rename('foo').select()
# from dataset array:
self.assertVariableEqual(
Variable(['w', 'x', 'y'], np.array([foo.values, bar.values])),
DataArray.concat([foo, bar], 'w'))
# from iteration:
grouped = [g for _, g in foo.groupby('x')]
stacked = DataArray.concat(grouped, self.ds['x'])
self.assertDataArrayIdentical(foo.select(), stacked)
