-(set! entities ((new-entity (make-a 1 2) (make-b)) entities))
-(set! entities ((new-entity (make-a 10 20)) entities))
-((new-entity (make-a 10 20)) entities)
-(test-eqv 2 (length (entity-list entities)))
+
+(receive (e k) (add-entities entity-set '((a . (1 2)) (b . #f)))
+ (set! entity-set e)
+ (set! key (car k)))
+(set! entity-set (add-entities entity-set '((a . (10 20)))))
+(add-entities entity-set '((a . (10 20))))
+(test-eqv 2 (entities-count entity-set))
+
+;; (define-component a x y)
+;; (define-component b)
+
+;; (define entities (make-entity-set))
+;; (define key #f)
+
+;; ; Modifying entities
+;; (define component (assoc-ref (get-entity entities key) 'a))
+;; (test-eqv 1 (a-x component))
+;; (test-eqv 2 (a-y component))