Spring – Unit testing a method dependent to the request context

I'm writing a unit test for a method that contains the following line:

String sessionId = RequestContextHolder.currentRequestAttributes().getSessionId();

I get the following error:

java.lang.IllegalStateException: No thread-bound request found: Are
you referring to request attributes outside of an actual web request,
or processing a request outside of the originally receiving thread? If
you are actually operating within a web request and still receive this
message, your code is probably running outside of
DispatcherServlet/DispatcherPortlet: In this case, use
RequestContextListener or RequestContextFilter to expose the current
request.

The reason is quite obvious — I'm not running the test in a request context.

The question is, how can I test a method that contains a call to a method dependent to the request context in a test environnment?

Thank you very much.