Unittesting Python class

Question

class Car:
 def __init__(self):
 self.__engine_size = 2.0
 self.__colour = str
 @property # getter
 def engine_size(self):
 return self.__engine_size
 @property # getter
 def colour(self):
 return self.__colour
 @colour.setter
 def colour(self, value):
 self.__colour = value
 def start(self):
 return 'Engine started!!....ggggrrrrrr'
 def stop(self):
 return 'Engine stopped!!...'

Hey guys, trying to perform a test on this piece of code but can't think of ways. See bellow what I did and suggest other ways if known.

import unittest
from car import __init__
class TestCarMethods(unittest.TestCase):
 # case assertion no1
 '''
 '''
 def test_car_colour(self):
 # arrange
 __engine_size = 3.2
 __colour = 'red'
 # act
 result = ('red')
 # assert
 self.assertEqual(result, 'red')
 if __name__ == '__main__':
 unittest.main()

• chepner: Don't use a property if the getter/setters just provide unrestricted or unmodified access to the underlying attribute; just use the attribute directly.
• danH: Good point! I get stuck with start - stop
• James Li: tests come out naturally by defining what should it do , but not true when you try saying how does it do. for your piece of code . valid test would be the return values of start/stop, exception checking can be addwed too.

Answer 1

You need to create and work with an instance of your class.

class TestCarMethods(unittest.TestCase):
 def setUp(self):
 self.car = Car()
 def test_car_color(self):
 self.assertEqual(self.car.color, 'red') # If the default is, in fact, red
 def test_set_color(self):
 self.car.color = 'blue'
 self.assertEqual(self.car.color, 'blue')
 def test_start(self):
 self.assertEqual(self.car.start(), 'Engine started!!....ggggrrrrrr')

• danH: Appreciated, and makes a lot of sense setting up, I get blocked in trying to perform a test on start / stop.
• chepner: See update; it's just a matter of calling the method and checking what it returns.
• danH: Gosh, I think I need a break :))) thanks man. for a weird reason I was complicating it thinking that the functions start/ stop is called after color is set .....