How to set a persistent header value in a test with chai-http?

I run a test which makes a user login, and in a response there is a token sent to user that is supposed to be used in next requests as a Authorization header.

I am looking at this http://ift.tt/2fpMT8g and seeing that I can persist cookies between tests in one session.

How can I set a header for agent and keep it between tests too?