How do I ensure that all controllers in an asp.net web-api service are configured correctly _in a single test class_?

How do I ensure that all controllers in an asp.net web-api service are
configured correctly _in a single test class_?

Dipping my toes into asp.net and mvc, more specifically the web-api (2.0)
part of MVC 5, I like the idea of using attributes and creating your own
attribute classes to control how requests are handled and responses
returned for all api end-points.
The "How to test "Only certain roles should have access to a controller in
MVC" article describes how to unit test a single controller to ensure that
it keeps the correct attributes and doesn't get undesired attributes
added.
That is a perfectly valid way of unit testing individual controllers.
However, I prefer to have all tests of the API configuration in a single
place instead of spread around unit tests of individual controllers.
Especially as using attribute routing, a controller can very easily be
replaced by a different controller which may not have the correct
attributes and whose test companion doesn't test for them.
What I envision is a single test class where all aspects of the API
configuration can be secured against undesired effects of (inadvertent)
changes. What I am struggling with is how to set this up. Bryan Avery's
article (mentioned above) shows how to get a list of the custom attributes
of a controller class, but:
how do I get my hands on a list of all controllers present in the test
project?