I have been experimenting with several acceptance test frameworks for Java during the last few weeks (e.g. Fitnesse, JBehave).
Before deciding which one to use I tried to find out whether there are any commercial alternatives but did not really find any. Any pointers appreciated.
Our requirements are (incomplete and unsorted list):
For commercial alternatives:
Those are the only two I know about. Neither have large followings in the BDD community. I believe the two most-used tools are JBehave and Cucumber (which as @kazakovs points out is also available for the JVM). These help to capture English-language scenarios which would be readable by both developers and business analysts. I've also used (the .NET equivalent of) Fitnesse with Slim behind it; a quick bit of CSS makes it look like the others, while allowing for tables as well.
However, most BDD tools are designed for full-stack, system-wide scenarios, usually with nothing mocked out, or possibly with third-party libraries replaced by a custom framework. Mocking libraries don't really have the set-up to work at this scale.
If you're looking to integrate Mockito and JUnit, it sounds as if you might be trying to do BDD at a smaller scale, with classes or small groups of classes. This is how BDD originally started and is perfectly valid.
Since BDD's inception, tools like JUnit have improved, and Mockito didn't exist! So BDD tools are no longer particularly necessary. For class level code, I would be happy to simply use comments with Given, When and Then in place, like this (this is C# but Java would be similar).
As an alternative at a higher level, you can always knock up a small DSL. This didn't take me very long, and it's readable, even for non-technical business people. It runs using JUnit, and you could put Mockito in there if you wanted (but I still suspect you're mixing concerns if you want to do this).
Another benefit of the DSL is that it's a quick, cheap way to get started, with none of the set-up overhead of Cucumber or JBehave; but the steps produced are easily ported to something like JBehave later on (you just move the code to JBehave's regex steps, and I'd be surprised if you couldn't do something similar with Twist). Since you're uncertain about your requirements, I would recommend this route as it will help you to get started and get more information about what you do need, very cheaply.