yum clean all, but for a desired repo

[Peter Gueckel]

yum clean all clears all the information for all enabled repos.

How would one clean the information for only one of the enabled repos?

Say, I know that rpmfusion-free and fedora have not changed, but I already know 
that updates-testing has changed and I want to force yum to reload the 
information for only that one repo, but not bother reloading the information for 
the other repos.