---
tags: [python]
---

An instance of the general Python `Mock` that is pre-configured with "magic"
methods that the standard `Mock` lacks.

These methods mean that it can automaticaly behave like the following objects
without special configuration:

- a [context manager](./Using_a_context_manager_in_Python.md)
  - supports `__enter__`, `__exit__` and `with` statement

- a list or other container
  - supports `__iter__`, `__getitem`, `__len__`

- calls to a methods

## Example: mocking return from API call

Mock:

```py
def get_user_data(api_client):
    response = api_client.get_user(id=123)
    return response

```

As follows:

```py
from unittest.mock import MagicMock

def test_get_user_data():
    mock_api = MagicMock()
    mock_api.get_user.return_value = {"name": "Alice", "role": "Admin"}
    result = get_user_data(mock_api)

    assert result["name"] == "Alice"
    mock_api.get_user.assert_called_once_with(id=123)
```

## Example: testing behaviour of code that relies on context managers:

```py
def log_to_file(file_system):
    with file_system.open("log.txt") as f:
        f.write("Hello World")

def test_log_to_file():
    mock_fs = MagicMock()

    log_to_file(mock_fs)

    mock_fs.open.assert_called_with("log.txt")
    mock_fs.open().__enter__().write.assert_called_with("Hello World")
```