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The code generation templates and the runtime library itself are essentially feature complete with respect to the reference Java version. There are currently zero automated tests written and it isn't yet clear how such tests can/should be written (we suspect this applies to all the other targets too). In any case, some basic sanity check are done with samples grammars in the examples-v3 archive.
UPDATE: Just learned that some of the other targets have some automated unit tests already. We'll have a peek and see if this can be applied to C# too.
Architecture
The C# code generation and runtime are based on the Java version and would remain so until well after the final release. ANTLR 3 development (including AntlrWorks debugging support and some of the internal interfaces) is still so fluid that investing significant effort in developing radically different code output would be a little premature at this stage. That would be left as an exercise to the reader 
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