anchor.diff:              | Right facet ->
                   let entityDispatchers = World.getEntityDispatchers world
                   if World.isFacetCompatibleWithEntity entityDispatchers facet entityState then
  -                    let facetNames = Set.add facetName entityState.FacetNames
  -                    let facetsNp = facet :: entityState.FacetsNp
  -                    let entityState = { entityState with FacetNames = facetNames }
  -                    let entityState = { entityState with FacetsNp = facetsNp }
  +                    let entityState = { entityState with FacetNames = Set.add facetName entityState.FacetNames }
  +                    let entityState = { entityState with FacetsNp = facet :: entityState.FacetsNp }
                       let entityState = Reflection.attachProperties EntityState.copy facet entityState
                       match optEntity with
                       | Some entity ->
  
positive.code:                         let entityState = World.getEntityState entity world
                          (entityState, world)
                      | None -> (entityState, world)
                  let facetNames = Set.remove facetName entityState.FacetNames
                  let facetsNp = List.remove ((=) facet) entityState.FacetsNp
                  let entityState = { entityState with FacetNames = facetNames }
                  let entityState = { entityState with FacetsNp = facetsNp }
                  let propertyNames = World.getEntityPropertyDefinitionNamesToDetach entityState facet
                  let entityState = Reflection.detachPropertiesViaNames EntityState.copy propertyNames entityState
                  match optEntity with
                  | Some entity ->
                      let oldWorld = world
  
negative.code:                 List.notExists
                      (fun definition ->
                          match Xtension.tryGetProperty definition.PropertyName entityState.Xtension with
                          | Some property -> property.PropertyType <> definition.PropertyType
                          | None -> false)
                      facetPropertyDefinitions
              else false
  