unittest.mock断言错误：预期与实际调用不符问题求助

Hey there! Let's work through fixing that AssertionError: Expected and actual call not same issue you're hitting with unittest.mock. First, let's recap your setup to make sure we're on the same page:

Your Project Structure #

project/
├── src/
│   ├── __init__.py
│   └── function.py
└── tests/
    ├── __init__.py
    └── test_function.py

Your Test Code Snippet #

import unittest
from unittest import mock
from ..src.function import get_subscriptions
from ..src import function

class TestCheckOrder(unittest.TestCase):
    @mock.patch.object(function, 'table')
    def test_get_subscriptions_success(self, mocked_table):
        # ... your test logic here ...
        # Throws AssertionError: Expected and actual call not same

This error almost always boils down to a mismatch between what you expected your mocked table to be called with, and what it was actually called with during the test. Let's break down the most common fixes:

1. Verify Call Parameters Match

The #1 culprit is mismatched arguments. For example, if you wrote mocked_table.assert_called_with(123) but your actual code calls table(456, "extra_param"), the assertion will fail.

Fix:
Add a print statement to see exactly how table was called, then adjust your assertion to match:

def test_get_subscriptions_success(self, mocked_table):
    # ... run your test logic ...
    print("Actual call details:", mocked_table.call_args)  # This shows the real arguments
    # Update your assertion to match the output from the print statement
    mocked_table.assert_called_with(user_id=1, status="active")  # Example matching args

2. Ensure You're Patching the Right Object

Sometimes the patch targets the wrong instance of table. If get_subscriptions imports table from a different module than the one you're patching, your mock won't take effect.

Fix:
Double-check that you're patching the exact table object used by get_subscriptions. If get_subscriptions lives in src/function.py and uses the local table variable there, your current patch (@mock.patch.object(function, 'table')) is correct—but make sure you're running tests from the project root (use python -m unittest tests.test_function instead of running the test file directly) to avoid import path issues.

3. Check for Multiple Calls or Wrong Call Order

If you're using assert_called_once_with(...) but table gets called multiple times, or if you're asserting the wrong call in a sequence, you'll get this error.

Fix:
View all recorded calls with call_args_list to debug:

print("All calls to table:", mocked_table.call_args_list)
# If you just need to verify one of the calls matches, use:
mocked_table.assert_any_call(expected_arg1, expected_arg2)

4. Confirm Mock Return Values Are Set Correctly

If you didn't set a return value for mocked_table, your code might take an unexpected path that changes how table is called later.

Fix:
Set a realistic return value before running your test function:

def test_get_subscriptions_success(self, mocked_table):
    # Set mock return value to match what your code expects
    mocked_table.return_value = {"subscriptions": ["basic", "premium"]}
    # Run the function under test
    result = get_subscriptions(user_id=123)
    # Now assert the call
    mocked_table.assert_called_with(user_id=123)

Example Fixed Test Code #

Putting it all together, here's a revised version of your test with debugging and proper setup:

import unittest
from unittest import mock
from ..src.function import get_subscriptions
from ..src import function

class TestCheckOrder(unittest.TestCase):
    @mock.patch.object(function, 'table')
    def test_get_subscriptions_success(self, mocked_table):
        # Configure mock behavior
        mocked_table.return_value = {"user_id": 1, "subscriptions": ["premium"]}
        
        # Execute the function we're testing
        result = get_subscriptions(user_id=1)
        
        # Debug: print actual call to verify
        print("Actual call args:", mocked_table.call_args)
        
        # Assert the mock was called correctly
        mocked_table.assert_called_with(user_id=1)
        
        # Verify the function returns the expected result
        self.assertEqual(result, ["premium"])

Remember to run your tests from the project root directory to avoid relative import errors. If you're using pytest, add the -s flag to see the print output.

内容的提问来源于stack exchange，提问作者Vivek