Why do I receive the following AttributeError when testing a class method with unittest: 'class' object has no attribute 'testing method'?

Question

For the sake of practicing to code, I am trying to program a very simple game. When trying to run a test on a (private) class method, I receive the following error: AttributeError: 'LivingBeing' object has no attribute '_Test_Class_Methods__lose_hp'

More elaborate:

I have a class named "LivingBeing" in the file classes.py.

class LivingBeing:

def __init__(self, name, hp=100):
    self.name = name
    self.hp = hp

def __lose_hp(self, number=20, decimal_percentage=1):
    self.hp = self.hp - (21 - number)*decimal_percentage
    return self.hp

Now I would like to test said __lose_hp method, and I tried this with the following code:

import sys, unittest
sys.path.append("/Users/angel/OneDrive/Dokumente/Studium/CL/Programmieren/git_projects/fantasticgame/")

from classes import LivingBeing

class Test_Class_Methods(unittest.TestCase):

    def setUp(self):
        self.livingbeing = LivingBeing("Life")

    def test_lose_hp(self):
        self.assertEqual(self.livingbeing.__lose_hp(20), 99, "Should be 99")

if __name__ == "__main__":
    unittest.main()

What I tried so far:

• I found some information that it was most likely an ImportError, so I tried the "sys.path.append"-statement according to how a similar problem was solved. So, if I were to leave it out, I would receive the same error message. The file "classes.py" and the testing file are in this same folder.

• At first, I did not have the setUp method, however it had solved a somewhat similar problem for someone else (namely here), so I tried it - same error message for me however.

• I also didn't have the return statement in the class method itself at first, about which I very much understand why it would throw an Error by now (because the return value would be None).

• The very classic try to just restart (the computer) and retry before posting also did not help.

• There was a point at which I tried to make "Test_Class_Methods"
  inherit from both, the unittest.Testcase and LivingBeing, but this
  caused the same error again.

Looked like this:

class Test_Class_Methods(unittest.TestCase, LivingBeing):

    def setUp(self):
        self.livingbeing = LivingBeing("Life")

    def test_lose_hp(self):
        self.assertEqual(self.livingbeing.__lose_hp(20), 99, "Should be 99")

This being my first question, I hope it's as complete and concise as it should be, and I am thankful for any pointers to help with said error.

EDIT: I changed the method to being public instead of private, and with that change, it now works. If I happen to find a good guide on how to write tests for private methods, I might link it here for future answer-seekers.

Answer 1

I know it's a bit too late but I was facing the same AttributeError as yours. Removing double underscore from the beggining of the function I wanted to test helped me.