[epicide]

Keeps things that are coupled closer together. This is beneficial for several reasons:

a) forces parity between your code structure and test structure.

b) restructuring takes potentially half the time.

c) easily see and navigate to tests for a file.

d) less named things in your project since you aren't duplicating your structure.

If your directories are getting too lengthy to look at with tests in them, you should restructure them.

Edit: formatting and additional reason.