unittest: MagicMock-ed Method Fails Assertion #100417

armartirosyan · 2022-12-21T23:09:24Z

Bug report

Nested method fails assertion. More details are in the Environment section

Environment

Files

$ tree
.
├── module.py
└── test_azure_blob.py

module.py

from azure.storage.blob import BlobServiceClient

class AzureBlob:
    def __init__(self):
        self.blob_service_client = BlobServiceClient.from_connection_string("AZURE_STORAGE_CONNECTION_STRING")
        self.container = self.blob_service_client.get_container_client("AZURE_CONTAINER_NAME")

test_azure_blob.py

class TestAzureBlob (unittest.TestCase):

    @patch("module.BlobServiceClient")
    def test_AzureBlob(self, mock_Blob):

        azure_blob = AzureBlob()
        print(mock_Blob)
        print(mock_Blob.mock_calls)
        print(mock_Blob.from_connection_string.mock_calls)
        print(mock_Blob.from_connection_string.get_container_client.mock_calls)
        mock_Blob.from_connection_string.get_container_client.assert_called_once()

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

When tested assertion fails. Traceback is below

$ python -m unittest test_azure_blob.py 
<MagicMock name='BlobServiceClient' id='140122935218912'>
[call.from_connection_string('AZURE_STORAGE_CONNECTION_STRING'),
 call.from_connection_string().get_container_client('AZURE_CONTAINER_NAME'),
 call.__str__()]
[call('AZURE_STORAGE_CONNECTION_STRING'),
 call().get_container_client('AZURE_CONTAINER_NAME')]
[]
F
======================================================================
FAIL: test_AzureBlob (test_azure_blob.TestAzureBlob)
----------------------------------------------------------------------
Traceback (most recent call last):
  File "/home/user/.pyenv/versions/3.9.1/lib/python3.9/unittest/mock.py", line 1337, in patched
    return func(*newargs, **newkeywargs)
  File "/home/user/Projects/test_azure_blob/test_azure_blob.py", line 23, in test_AzureBlob
    mock_Blob.from_connection_string.get_container_client.assert_called_once()
  File "/home/uaser/.pyenv/versions/3.9.1/lib/python3.9/unittest/mock.py", line 886, in assert_called_once
    raise AssertionError(msg)
AssertionError: Expected 'get_container_client' to have been called once. Called 0 times.

----------------------------------------------------------------------
Ran 1 test in 0.003s

FAILED (failures=1)

As the prints are showing, the MagicMock identified that the get_container_client nested method was called, but the actual call fails the assertion.

CPython versions tested on: [3.9.1, 3.10.2]
Operating system and architecture:[Ubuntu x86, Windows x86]

The text was updated successfully, but these errors were encountered:

carljm · 2022-12-22T01:59:35Z

You need to change the assertion to look for mock_Blob.from_connection_string.return_value.get_container_client.assert_called_once() -- note the added .return_value. get_container_client is an attribute of the mock returned by calling from_connection_string, it's not an attribute of from_connection_string.

Note that your debug prints also confirm this; the calls are recorded on from_connection_string().get_container_client(...) (note the parentheses); when you print mock_Blob.from_connection_string.get_container_client.mock_calls it is (correctly) empty.

armartirosyan added the type-bug An unexpected behavior, bug, or error label Dec 21, 2022

carljm closed this as completed Dec 22, 2022

carljm reopened this Dec 22, 2022

carljm closed this as not planned Won't fix, can't repro, duplicate, stale Dec 22, 2022

unittest: MagicMock-ed Method Fails Assertion #100417

unittest: MagicMock-ed Method Fails Assertion #100417

armartirosyan commented Dec 21, 2022

carljm commented Dec 22, 2022

unittest: MagicMock-ed Method Fails Assertion #100417

unittest: MagicMock-ed Method Fails Assertion #100417

Comments

armartirosyan commented Dec 21, 2022

Bug report

Environment

carljm commented Dec 22, 2022