anchor.diff:  
       member self.describe (name: string) (f: unit -> unit) = 
           let oldContext = context
  -        context <- TestContext.create name (Some(context))
  +        context <- TestContext.create name
           f()
           context <- TestContext.addChildContext oldContext context
   
  
positive.code:         ChildContexts : T list;
          }
  
      let create name parent = { 
          Name = name;
          Tests = [];
          Setups = [];
  
negative.code:         )
  
  type TestCollection() =
      let mutable context = TestContext.create null
  
      member self.init (f: unit -> 'a) : (unit -> 'a) =
          let value = ref None
  