title: Python, unit-testing and mocking imports
body: <p>I am in a project where we are starting refactoring some massive code base. One problem that immediately sprang up is that each file imports a lot of other files. How do I in an elegant way mock this in my unit test without having to alter the actual code so I can start to write unit-tests?</p>
  
  <p>As an example: The file with the functions I want to test, imports ten other files which is part of our software and not python core libs.</p>
  
  <p>I want to be able to run the unit tests as separately as possible and for now I am only going to test functions that does not depend on things from the files that are being imported.</p>
  
  <p>Thanks for all the answers. </p>
  
  <p>I didn't really know what I wanted to do from the start but now I think I know. </p>
  
  <p>Problem was that some imports was only possible when the whole application was running because of some third-party auto-magic. So I had to make some stubs for these modules in a directory which I pointed out with sys.path</p>
  
  <p>Now I can import the file which contains the functions I want to write tests for in my unit-test file without complaints about missing modules.</p>