Integration testing is hard but essential. It is hard to track down integration issues (due to a misunderstanding between the callee and the caller's contract/API/service) but that's where most of bugs are located from my own experience.
Unit tests with mocking does not help. Who cares about my expectations about what a contrat/API/service provides if it does not match the actual implementation. Testing in situ is the best way to check the actual behavior.
Arquillian is a fantastic tool to help write, execute and maintain integration tests.
Congratulations to the Arquillian team!