docs: function () { $assertEveryCalled (function (early, lately) {
          
          var compo = $singleton (Component, {
                          hasMessage: $barrier () })
  
          compo.hasMessage (function (_msg) { $assert (_msg, 'mkay'); early () })
          compo.hasMessage ('mkay')
          compo.hasMessage (function (_msg) { $assert (_msg, 'mkay'); lately () }) }) }