Unable to mock a python function return value using patch

Question

I have 2 files and a test file. For some unknown reason, i could not get this to pass. This tests always fail as it still returns 'hello_world' instead of using the mocked value of 'goodbye_world'.

utils.py

def hello_world():
    return "hello_world"

foo.py

from utils import hello_world
class Foo:
    def function_a():
        return hello_world()

test.py

import foo
from unittest.mock import patch
from unittest import TestCase

class TestStuff(TestCase):
  @patch('foo.hello_world')
  def test_hello_world(mock_value):
      mock_value.return_value = 'goodbye_world'
      temp = foo.Foo()
      self.assertEqual(temp.function_a(), 'goodbye_world')

Answer 1

Oh i figured it out. I should be patching from the src directory. So it should be 'src.foo.hello_world'