pytest-mock is currently the #3 pytest plugin. 
pytest-mock is a wrapper around unittest.mock.

In this episode:

• Why the pytest-mock plugin is awesome
• What is mocking, patching, and monkey patching
• What, if any, is the difference between mock, fake, spy, stub. 
• Why we might need these in testing
• Some history of mock in Python and how mock became unittest.mock
• From unittest.mock
  • patch.object
  • patch.object with autospec
  • using these as context managers
• pytest-mock:
  • The mocker fixture 
  • Cleanup in teardown
  • Using mocker.patch, mocker.spy, and mocker.stub
  • Why it's awesome and why you might want to use it over straight unittest.mock

Links:

• top pytest plugins list
• pytest-mock documentation
• unittest.mock
• Podcast episode discussing unittest.mock with Michael Foord
• monkeypatch