More subtests

class:
* class statements are block-scoped
* implicit strict mode

super:
* in constructors
* in methods
* statically bound

arrows:
* "this" unchanged by Function#call or Function#apply.

Map/Set/WeakMap/WeakSet:
* constructor arguments
* #size 
* #delete 
* #clear 
* #forEach 
* #keys 
* #values 
* #entries