Tests separate from your code

An alternative to the method above is to organize your tests in a separate directory from the main package:

setup.py
mylib/  
    __init__.py
    core.py
    utils.py
tests/
    __init__.py
    test_core.py
    test_utils.py 

Some people prefer this layout because:

• It keeps library code and testing code separate
• The testing code is not included in the source package

One disadvantage of the above method is that, once you have a more complex hierarchy, you will probably want to keep the same hierarchy inside your tests directory, and that's a little harder to maintain and keep in sync:

mylib/  
    __init__.py
    core/
        __init__.py
        foundation.py
    contrib/
        __init__.py
        text_plugin.py
tests/
    __init__.py
    core/
        __init__.py
        test_foundation.py
    contrib/
        __init__.py
        test_text_plugin.py