10. Mocking in Unit Tests

These snippets showcase a variety of ways to use unittest.mock for testing in Python, including mocking functions, classes, attributes, and dependencies, as well as asserting calls and handling side effects.

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1. Mocking a Simple Function

from unittest.mock import Mock

# Original function
def greet():
    return "Hello!"

# Mock the function
mock_greet = Mock(return_value="Hi there!")
print(mock_greet())  # Output: Hi there!

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2. Mocking Method Calls in a Class

from unittest.mock import MagicMock

class MyClass:
    def method(self):
        return "Real method"

obj = MyClass()
obj.method = MagicMock(return_value="Mocked method")
print(obj.method())  # Output: Mocked method

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3. Asserting Function Calls

from unittest.mock import Mock

mock_func = Mock()
mock_func(42)
mock_func.assert_called_with(42)  # Passes if called with 42

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4. Mocking a Module Dependency

from unittest.mock import patch

# Original function
def get_data():
    import requests
    response = requests.get("http://example.com")
    return response.status_code

# Mocking requests.get
with patch("requests.get") as mock_get:
    mock_get.return_value.status_code = 200
    print(get_data())  # Output: 200

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5. Mocking an Object Attribute

from unittest.mock import patch

class MyClass:
    attribute = "Original value"

with patch.object(MyClass, "attribute", "Mocked value"):
    print(MyClass.attribute)  # Output: Mocked value

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6. Mocking a Class

from unittest.mock import patch

class MyClass:
    def method(self):
        return "Original method"

with patch("__main__.MyClass") as MockClass:
    instance = MockClass.return_value
    instance.method.return_value = "Mocked method"
    print(instance.method())  # Output: Mocked method

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7. Mocking with Side Effects

from unittest.mock import Mock

def side_effect_func(arg):
    return f"Processed {arg}"

mock = Mock(side_effect=side_effect_func)
print(mock("data"))  # Output: Processed data

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8. Mocking a Context Manager

from unittest.mock import MagicMock

mock_context = MagicMock()
mock_context.__enter__.return_value = "Inside the context"
mock_context.__exit__.return_value = None

with mock_context as value:
    print(value)  # Output: Inside the context

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9. Mocking Multiple Calls with Different Results

from unittest.mock import Mock

mock = Mock()
mock.side_effect = [1, 2, 3]
print(mock())  # Output: 1
print(mock())  # Output: 2
print(mock())  # Output: 3

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10. Using Mock in Unit Test Class

import unittest
from unittest.mock import patch

def get_user_info(user_id):
    import database
    return database.get_user(user_id)

class TestUserInfo(unittest.TestCase):
    @patch("database.get_user")
    def test_get_user_info(self, mock_get_user):
        mock_get_user.return_value = {"id": 1, "name": "John Doe"}
        user_info = get_user_info(1)
        self.assertEqual(user_info, {"id": 1, "name": "John Doe"})
        mock_get_user.assert_called_once_with(1)

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

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