def test_group():
col_ref = NamedCollection(*GROUP_DATA)
col1 = NamedCollection(*GROUP_DATA)
col1.group(['a'])
col2 = NamedCollection(*GROUP_DATA, group=['a'])
for col in [col1, col2]:
assert len(col) == 2
assert col[0]['a'] == 1
assert col[1]['a'] == 2
assert len(col[0].children) == 3
assert type(col) == type(col[0].children)
assert set(col[0].children) <= set(col_ref)
for row in col:
assert len(row) == 2