Codeception and Mocking

Hi, I am starting to use codeception and I currently have a functional test that checks a signup process. As part of the signup a user image is uploaded and then stored in S3. The tests work but take a few seconds so I would like to mock the S3 upload and test it separately.

The problem is that mocking the component doesn't seem to affect the actual signup process, presumably because its happening as a separate process.

Does anyone have any recommendations?

Thanks