Just another feature that you can decide HOW you want to use it!
For instance I use the "Testcase" object to map my End-to-End system tests that cross use cases.
For example:
Create Testcase named "Manage Loans", then I could create scenarios that could be "Process New Load Applications", "Send End of Loan Thank-Yous", "Send Need Another Loan Ticklers", etc.
Each of these scenarios would represent a business process, that is composed of several different types of interactions with the System Under Design (the UC's named scenarios). So then within the testcase, I would create a test for each testcase scenario I defined, and then build them up using references to the system use case scenarios that would be appropriate (e.g, UC A, Scenario 1 then UC D, Scenario 5, then UC B, Scenario 3, etc.) until the process has been defined... and now can be managed as a end-to-end test of the system...
EA has a very flexiable approach to testing, you just need to come up with a style/approach that works for you...