0 Go VM:
2 I don't know of any attempt to publish general test cases as a resource for developers, although I think that would be hugely valuable project (and I've made writing specifications and tests a high priority in BQN development). The biggest issue for making dialect-agnostic tests would probably be the primitives where symbols are completely different between dialects. One approach might be to write the tests using special unambiguous symbols, and convert them before running.
2 [APL](https://aplwiki.com) and APL-like languages (e.g. [J](https://aplwiki.com/wiki/J), [K](https://en.wikipedia.org/wiki/K_(programming_language)) and [Q](https://en.wikipedia.org/wiki/Q_(programming_language_from_Kx_Systems))), along with [array programming](https://en.wikipedia.org/wiki/Array_programming) in any language (e.g. [NumPy](https://en.wikipedia.org/wiki/NumPy), [Julia](https://en.wikipedia.org/wiki/Julia_(programming_language)), and [MatLab](https://en.wikipedia.org/wiki/MATLAB)) (especially if in comparison to APLs).
1 APL only
1 There are [only 227](https://stackoverflow.com/questions/tagged/apl) questions tagged `apl` on SO. There are also (https://stackoverflow.com/questions/tagged/j) tagged `j` and (https://stackoverflow.com/questions/tagged/k) tagged `k`.