Remove sleep-based concurrency from newVertex test

Add a synchronization channel for the TestWalker_newVertex test, rather
than using a sleep and running it multiple times.

dag/walk_test.go

@@ -92,19 +92,33 @@ func TestWalker_error(t *testing.T) {
 }
 
 func TestWalker_newVertex(t *testing.T) {
-	// Run it a bunch of times since it is timing dependent
-	for i := 0; i < 50; i++ {
 	var g AcyclicGraph
 	g.Add(1)
 	g.Add(2)
 	g.Connect(BasicEdge(1, 2))
 
+	// Record function
 	var order []interface{}
-		w := &Walker{Callback: walkCbRecord(&order)}
+	recordF := walkCbRecord(&order)
+	done2 := make(chan int)
+
+	// Build a callback that notifies us when 2 has been walked
+	var w *Walker
+	cb := func(v Vertex) error {
+		if v == 2 {
+			defer func() {
+				close(done2)
+			}()
+		}
+		return recordF(v)
+	}
+
+	// Add the initial vertices
+	w = &Walker{Callback: cb}
 	w.Update(&g)
 
-		// Wait a bit
-		time.Sleep(10 * time.Millisecond)
+	// if 2 has been visited, the walk is complete so far
+	<-done2
 
 	// Update the graph
 	g.Add(3)
@@ -124,7 +138,6 @@ func TestWalker_newVertex(t *testing.T) {
 	if !reflect.DeepEqual(order, expected) {
 		t.Fatalf("bad: %#v", order)
 	}
-	}
 }
 
 func TestWalker_removeVertex(t *testing.T) {