How can I use advanced mocking techniques in pytest?

How can I use advanced mocking techniques in pytest?

You can use the unittest.mock library to create advanced mocks in pytest. This allows you to replace parts of your system under test and make assertions about how they were used.

Can you give me an example of mocking a function?

Sure! You can use mock.patch to replace a function with a mock. For example:

from unittest.mock import patch

@patch('module_name.function_name')
def test_function(mock_function):
    mock_function.return_value = 'mocked value'
    assert function_that_calls_function_name() == 'expected result'

What about mocking classes?

You can mock classes in a similar way. Use mock.patch to replace the class with a mock object. Here's an example:

from unittest.mock import patch

@patch('module_name.ClassName')
def test_class(mock_class):
    instance = mock_class.return_value
    instance.method.return_value = 'mocked method'
    assert instance.method() == 'mocked method'

How do I assert that a mock was called?

You can use the assert_called_once method on your mock object. For example:

mock_function.assert_called_once()