There are few tools like Rational Rhapsody by IBM, that helps you generate UML diagram. You can draw a state diagram from the description of the state of the unit. Test cases then are defined to exercise each path of the state. Test case even demonstrates the behaviors it should exhibit and assures that it should not exhibit that doesn't occur.
Rational Rhapsody is again a paid software and you will have to modify your test cases anyway.
P.S.: Nowadays, easier way to handle this is by making use of gherkin files. Gherkin is a Business Readable, Domain Specific Language created especially for behavior descriptions. It gives you the ability to remove logic details from behavior tests.
So, your BA will write software specification in Gherkin format. The same file can be used by testers and the automation engineers. And this way everyone will be in sync.
