If you haven't heard, the latest addition to the *Box family is TestBox and is currently out in Alpha. It allows for the standard xUnit style of testing that you may already be familiar with in tools like MXUnit. TestBox also allows for a newer style of testing known as Behavior-Driven Development or BDD. BDD helps focus on writing tests that confirm specific business needs are met by your software and typically use some sort of human-readable DSL that allows the test to be self-documenting and clear on what they are testing for in a way that translates nicely from your business specs.
TestBox's BDD runners are based on closures and only work on CF10 and Railo's latest. Here's an example:

function run(){

    describe("A suite", function(){
        it("contains a spec with awesome expectations", function(){
            expect( true ).toBeTrue();
            expect( [1,2,3] ).toBeArray();

            message = 'foo man choo'; 
            expect( message ).toMatch( '^foo' );
        });
    });

}

As you can see, the tests are very readable. In real world examples, you would focus your expect() and toXXX() methods on real business requirements that define the behavior of your models.

We also have complete backwards compatibility with MXUnit so you can switch immediately with zero test code changes!

Read up on TestBox here: http://wiki.coldbox.org/wiki/TestBox.cfm
Read our intro to BDD here: http://wiki.coldbox.org/wiki/TestBox-bdd-primer.cfm

P.S. In addition to allowing for complete extensibility in regards to assertions, test runners, and reporting, TestBox also has an asynchronous mode to speed up the time it takes to run your large test suites. http://wiki.coldbox.org/wiki/TestBox-BDD-Primer.cfm#Asynchronous_Testing