> we found that there are 17 semantic rules in the core semantics which are not covered by the [ECMAScript Conformance Test Suite]

> we succeeded to manually write test programs that hit 11 out of 17 behaviors

> the remaining 6 semantic behaviors are infeasible, that is, they represent flaws in the language standard itself

[0] https://github.com/kframework/javascript-semantics/blob/mast...