What git branch should I commit unit tests to?

I'm currently following the ever-popular git workflow described here.

One thing it doesn't discuss is how to handle unit testing. Let's say I write some code and commit to develop. I want to write a test for it, but I don't want it in my develop history, I'd like to keep the tests separate so that when I look at git log I only see changes to the main code. However, if I commit the test to a separate test branch, I'll have to merge develop/test back and forth constantly, resulting in a ridiculous amount of merge commit clutter.

How do you manage unit testing in a git repository?