Mocked Class & Asserting Method Calls

Question

Stumped on how to mock a class and be able to assert that its' methods are called with some arguments. When I assert the call i get a "Not called" assertion but, I can see the method call in the mock_calls attribute.

sandbox/module.py

class Subject(object):
    def __init__(self):
        pass

    def run(self, *args, **kwargs):
        reference = Reference(*args, **kwargs)
        reference.method_a(*args)


class Reference(object):
    def __init__(self, *args, **kwargs):
        pass

    def method_a(self, *args):
        pass

test.py

import unittest
from unittest import mock
from sandbox.module import Subject


class TestSandbox(unittest.TestCase):

    @mock.patch('sandbox.module.Reference')
    def test_method_calls(self, mock_reference):
        subject = Subject()
        subject.run(1, 2, 3, x=44, y=55, z=66)
        mock_reference.assert_called_with(1, 2, 3, x=44, y=55, z=66)
        mock_reference.method_a.assert_called_with(1, 2, 3)

The result is

AssertionError: Expected call: method_a(1, 2, 3)  
Not called

The value of mock_reference.mock_calls is

[
    call(1, 2, 3, x=44, y=55, z=66), 
    call().method_a(1, 2, 3)
]

If I access call as call().method_a I can access the method details but, the mock_calls gets a item call() added to it. Which could change assert_called_once_with in a way i wouldn't expect and, doesn't feel quite right. Furthermore, if autospec=True is used I need to pass the params again. Using just call as in mock_reference.call.method_a does not work either.

Output of mock_calls when accessing call().method_a.mock_calls

mock_reference().method_a.mock_calls

[
    call(1, 2, 3, x=44, y=55, z=66), 
    call().method_a(1, 2, 3),
    call()
]    

mock_reference.assert_called_once_with(1, 2, 3)

AssertionError: Expected 'Reference' to be called once. Called 2 times.

Answer 1

You mocked a class, yet the second method is called on instance. Change

mock_reference.method_a.assert_called_with(1, 2, 3)

to

mock_reference.return_value.method_a.assert_called_with(1, 2, 3)