Mocking class attribute that is a class imported from another module unittest python-CodePudding

I have following project structure:

├───pa
│   |───__init__.py
|   |─── a1.py
|   |─── test_a1.py
|
├───pb
│   |───__init__.py
|   |─── b1.py

With following code: b1.py:

class B1:

    def __init__(self):
        self.text = "Unmocked_B1"

    def get_text(self):
        return self.text

pb.__init__.py:

from .b1 import B1

a1.py:

from src.pb import B1


class A1:

    def __init__(self):
        self.b = B1()

    def get_text(self):
        return self.b.get_text()

pa.__init__.py:

from .a1 import A1

And I want to mock self.b in class A1 using unittest.mock.patch in such way that following code in test_a1.py will print "Mocked B1"

test_a1.py:

from unittest import TestCase
from unittest.mock import patch, PropertyMock
from . import A1


class TestB1(TestCase):

    @patch('Some args')
    def test_get_text(self, mocked_b1):
        # Some code
        
        a1 = A1()
        print(a1.get_text())  # Should print: Mocked B1

I tried both mocking B1 import with:

@patch('src.pb.b1.B1')
    def test_get_text(self, mocked_b1):
        mocked_b1.get_text.return_value = 'Mocked B1'

        a1 = A1()
        print(a1.get_text())  # Should print: Mocked B1

And mocking property of a1 with property mock:

@patch('pa.a1.A1.b', new_callable=PropertyMock)
    def test_get_text(self, mocked_b):
        mocked_b.get_text.return_value = 'Mocked B1'

        a1 = A1()
        print(a1.get_text())  # Should print: Mocked B1

Which does not seem to work even when I make attribute b inside A1 static instead of dynamic.

Is there a way to mock this attribute? It would be perfect if it would work on dynamic attribute as shown earlier.

I'm using python 3.10

CodePudding user response：

Try the following sintax that uses patch.objectand context manager (instruction with):

class TestB1(TestCase):
    def test_get_text(self):
        a1 = A1()
        with patch.object(a1, "b") as mocked_b1:
            mocked_b1.get_text.return_value = 'Mocked B1'

            print(a1.get_text())  # Prints: Mocked B1

CodePudding user response：

Thank you frankfalse for answer of course similar solution with patch decorator also works (I discovered it this morning):

@patch('src.pa.a1.B1')
def test_get_text(self, mocked_B1):
    instance = mocked_B1.return_value
    instance.get_text.return_value = 'Mocked B1'

    a1 = A1()
    print(a1.get_text())  # Prints: Mocked B1

Don't know if there is solution with property mock