fix

lib/Graph.ts

@@ -75,6 +75,7 @@ export class Graph extends Element {
 
   public add_graph (constructor: ((g: Graph) => void) | string): string {
     const graph = new Graph ('unnamed', this.full_name);
+    graph.directional = this.directional;
 
     if (typeof constructor === 'string')
       graph.name = constructor;

test/Graph.ts

@@ -26,6 +26,19 @@ const result = `digraph foo {
   foo_foo -> foo_baz
 }`;
 
+const non_directional = `graph foo {
+  subgraph cluster_foo_bar {
+    foo_bar_baz [label="baz"]
+    foo_bar_asd [label="asd"]
+
+    foo_bar_baz -- foo_bar_asd
+  }
+
+  foo_foo [label="foo"]
+
+  foo_bar_baz -- foo_foo
+}`;
+
 test ('serialize', (t) => {
   const g = new Graph ('foo');
 
@@ -63,3 +76,23 @@ test ('serialize', (t) => {
 
   t.is (serialized, result);
 });
+
+test ('non directional', (t) => {
+  const g = new Graph ('foo');
+  g.directional = false;
+
+  let n = '';
+
+  g.add_graph ((sub) => {
+    sub.name = 'bar';
+    n = sub.add_node ('baz');
+    const n2 = sub.add_node ('asd');
+
+    sub.add_edge (n, n2);
+  });
+
+  const f = g.add_node ('foo');
+  g.add_edge (n, f);
+
+  t.is (g.toString (), non_directional);
+});