def test_traverse():
t = TableSymbol('t', '{name: string, amount: int}')
assert t in list(t.traverse())
expr = t[t['amount'] < 0]['name']
trav = list(expr.traverse())
assert any(t['amount'].isidentical(x) for x in trav)
assert any((t['amount'] < 0).isidentical(x) for x in trav)
