def test_add_animal():
exp = Experiment()
exp.add_animal("dog")
exp.add_animal("cat")
assert exp.animals == ["dog", "cat"]
exp.add_animal("frog")
exp.add_animal("cat")
assert exp.animals == ["dog", "cat", "frog"]
def test_add_constraint():
c1 = ("dog", "in front of", "frog")
exp = Experiment(["dog"])
exp.add_constraint(c1)
assert exp.animals == ["dog", "frog"]
assert exp.constraints == [c1]
