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Sarj Sarj Sarj Standards

mock-without-spec

Unrestricted mock permits attributes outside the collaborator contract.

SARJ040 Rule source Tests Catalog JSON

Why

A mock without a spec permits removed or misspelled attributes; a callable mock without autospec may also accept stale call shapes.

Fix

Use spec_set=RealType or a concrete fake for collaborators, autospec=True for patched callables, and create_autospec when direct-call signatures matter. Use object() or mock.sentinel for identity markers.

Examples

Before — flagged Mock accepts any attribute
tests/test_service.py
from unittest.mock import Mock




def test_service():
    client = Mock()
    client.send()  # A typo or removed method still passes.
After — preferred Autospecced mock follows attributes and signatures
tests/test_service.py
from unittest.mock import create_autospec




def test_service():
    client = create_autospec(Client, instance=True, spec_set=True)
    client.send()
Before — flagged Patch generates an unrestricted replacement
tests/test_service.py
from unittest.mock import patch




def test_service():
    with patch("app.client.Client.send") as send:
        run_service()
        send.assert_called_once()
After — preferred Patch preserves the callable contract
tests/test_service.py
from unittest.mock import patch




def test_service():
    with patch("app.client.Client.send", autospec=True) as send:
        run_service()
        send.assert_called_once()