diff --git a/bn-tests.rkt b/bn-tests.rkt
index e7b81a2..b839e87 100644
--- a/bn-tests.rkt
+++ b/bn-tests.rkt
@@ -16,7 +16,7 @@
            [f2 (λ ([s : State])
                  (let ([x2 (hash-ref s 'x2)])
                    (not x2)))]
-           [bn (hash 'x1 f1 'x2 f2)])
+           [bn (make-bn `((x1 . ,f1) (x2 . ,f2)))])
 
       (test-case "One-step syncronous update"
         (let* ([s (new-state '((x1 . #t) (x2 . #f)))]
diff --git a/bn.rkt b/bn.rkt
index e56d39a..2112596 100644
--- a/bn.rkt
+++ b/bn.rkt
@@ -8,7 +8,7 @@
 ;;; The variables to be updated at each step are given by the mode.
 
 (provide Variable State UpdateFunc Network
-         update new-state)
+         update new-state make-bn)
 
 (define-type Variable Symbol)
 
@@ -38,3 +38,7 @@
 ;;; A version of make-hash restricted to creating Boolean states.
 (define (new-state [mappings : (Listof (Pairof Variable Boolean))])
   (make-hash mappings))
+
+;;; A version of make-hash restricted to creating Boolean networks.
+(define (make-bn [funcs : (Listof (Pairof Variable UpdateFunc))])
+  (make-hash funcs))