GTest is an easy to use framework that is relatively portable and doesn't carry around to many dependencies.
It won't allow you to do anything overly fancy, but I've always found it extremely easy to use, generic to work with any project, and takes minimal amounts of setting up. It also works in conjunction with GMock to add support for mocks which is always nice. It takes a little over ten minutes to set up and compile. From there it's extremely easy to setup a test bed and it is easily extendable.
Here's a link to the sample page. https://code.google.com/p/googletest/source/browse/trunk/samples/sample1_unittest.cc