def test_mammal_class(self):
"""Test case:
* Mammal should have a method called 'speak' that returns 'hello'.
* Mammal should have a method called 'legs' that returns 2.
* The output of 'legs' can be overwritten by modifying the _legs attribute of the Mammal class.
"""
mammal = Mammal()
self.assertEqual(mammal.speak(), 'hello')
self.assertEqual(mammal.legs(), 2)
mammal._legs = 4
self.assertEqual(mammal.legs(), 4)
def test_dog_class(self):
"""Test case:
* Dog's speak method should return 'arf'.
* Dog's 'legs' method should return the output of Mammal's legs method multiplied by 2.
"""
mammal = Mammal()
dog = Dog()
self.assertEqual(dog.speak(), 'arf')
self.assertEqual(dog.legs(), mammal.legs()*2)
