title: Set HTTP headers for all requests in a Flask test
body: <p>I'm using Flask and have endpoints which require authorization (and occasionally other app-specific headers). In my tests use the <code>test_client</code> function to create a client and then do the various get, put, delete calls. All of these calls will require authorization, and other headers to be added. How can I setup the test client to put such headers on all of the requests?</p>