def test_birth_weight_loss():
"""Does birthing an animal reduce the animals weight to a non-negative number?"""
h1 = Herbivore(weight=20)
h2 = Herbivore()
h1.change_weight(h2.weight, True)
assert h1.weight < 20
assert h1.weight > 0
def test_natural_weight_loss():
"""Does animals lose weight each year as expected?"""
h = Herbivore()
weight_h = h.weight
h.change_weight()
assert weight_h - (h._ani_params['eta'] * weight_h) == h.weight
c = Carnivore()
weight_c = c.weight
c.change_weight()
assert weight_c - (c._ani_params['eta'] * weight_c) == c.weight
def test_herbivore_eating_weight_change():
"""Does herbivores gain weight correctly?"""
h1 = Herbivore()
weight = h1.weight + 10 * h1._ani_params['beta']
h1.change_weight(10)
assert weight == h1.weight
