diff --git a/networks-tests.rkt b/networks-tests.rkt
index a94d7af..8d0a637 100644
--- a/networks-tests.rkt
+++ b/networks-tests.rkt
@@ -84,7 +84,8 @@
   (let* ([n #hash((a . (not b)) (b . a))]
          [doms (make-boolean-domains '(a b))]
          [sig1 (build-signed-interaction-graph/form n doms)]
-         [sig2 (build-boolean-signed-interaction-graph/form n)])
+         [sig2 (build-boolean-signed-interaction-graph/form n)]
+         [sig3 (build-boolean-signed-interaction-graph (nn n))])
     (check-equal? (get-interaction-sign (nn n) doms 'a 'b) '+)
     (check-equal? (get-interaction-sign (nn n) doms 'b 'a) '-)
 
@@ -108,7 +109,14 @@
     (check-false (has-edge? sig2 'c 'b))
     (check-false (has-edge? sig2 'c 'a))
     (check-equal? (edge-weight sig2 'a 'b) '+)
-    (check-equal? (edge-weight sig2 'b 'a) '-)))
+    (check-equal? (edge-weight sig2 'b 'a) '-)
+
+    (check-true (has-vertex? sig3 'a))
+    (check-true (has-vertex? sig3 'b))
+    (check-equal? (edge-weight sig3 'a 'a) '+)
+    (check-equal? (edge-weight sig3 'b 'b) '+)
+    (check-equal? (edge-weight sig3 'a 'b) '+)
+    (check-equal? (edge-weight sig3 'b 'a) '-)))
 
 (test-case "Dynamics of networks"
   (check-equal? (pretty-print-state (st '((a . #f) (b . 3) (c . 4)))) "a:#f b:3 c:4")