def test_breadth_first_search():
section = ExperimentSection(make_tree(['session', 'block', 'trial'], {}), ChainMap())
section[1][2].data['foo'] = True
key = lambda node: node.data.get('foo', False)
search_result = section.breadth_first_search(key)
assert search_result == [section, section[1], section[1][2]]
assert section.breadth_first_search(lambda node: False) == []
