pytest-mock

pytest plugin

overview

• provides a new fixture for pytest called mocker which wraps the standard mock library
• undoes mocking automatically at the end of the test, apparently according to the documentation

installation

• pip install pytest-mock

usage

• example for mocking a function

  test_example.py

  import pytest
   
  from my_module import calculate
   
  class MockLogger:
  	def info(self, *args, **kwargs):
  		return "FOO"
   
  def test_example(mocker):
  	mock_calculate = mocker.patch('my_module.calculate')
  	mock_calculate.return_value = 42
   
  	# can do this as well
  	mocker.patch('my_module.procrastinate').return_value = "foo"
   
  	# to patch with a different module
  	mocker.patch('my_module.dev_logger', MockLogger)
   
  	result = calculate(2, 3)
  	assert result == 42

• example using django model

  test_example.py

  import pytest
   
  from app.models import ExampleModel
   
  # to patch the django model objects.get fn
  def test_example1(mocker):
  	mock_object = mocker.Mock(spec=ExampleModel)
  	mock_object_instance = mocker.patch.object(
  		ExampleModel.objects, "get"
  	)
  	mock_object_instance.return_value = mock_object
   
  	# another way to mock return_value for method inside a
  	# class
  	mock_object.method_in_class.return_value = "foo"
   
  # to raise an exception
  def test_example2(mocker):
  	mock_object_instance = mocker.patch.object(ExampleModel.objects, "get")
  	mock_object_instance.side_effect = ExampleModel.DoesNotExist