Python Testing with pytest

Avoiding Filename Collisions

The utility of having __init__.py files in every test subdirectory of a project confused me for a long time. However, the difference between having these and not having these is simple. If you have __init__.py files in all of your test subdirectories, you can have the same test filename show up in multiple directories. If you don’t, you can’t. That’s it. That’s the effect on you.

Here’s an example. Directory a and b both have the file, test_foo.py. It doesn’t matter what these files have in them, but for this example, they look like this:

ch6/dups/a/test_foo.py

def test_a():
    pass

ch6/dups/b/test_foo.py

def test_b():
    pass

With a directory structure like this:

dups
├── a
│   └── test_foo.py
└── b