def test_eval_set():
env = Environment([['a', 0]])
exp = ['set!', 'a', 10]
eval_in_env(exp, env)
assert env.lookup('a') == 10
def test_eval_define():
env = Environment([])
exp = ['define', 'a', 3]
eval_in_env(exp, env)
#assert env._env == [['a', 3]]
assert env.lookup('a') == 3