From d01b0b064798dc1373fd0081965f4cc992dc7cd1 Mon Sep 17 00:00:00 2001
From: James Bardin <j.bardin@gmail.com>
Date: Mon, 20 Feb 2017 15:18:25 -0500
Subject: [PATCH] Remove intermittent failure from newEdge test

Because the vertex visit was record after the Update call, Updated
vertices may have been visited before the visit was recorded, causing
occasional test failures.

The order is now deterministic, and we can remove the brute-force loop.
---
 dag/walk_test.go | 59 ++++++++++++++++++++++++------------------------
 1 file changed, 29 insertions(+), 30 deletions(-)

diff --git a/dag/walk_test.go b/dag/walk_test.go
index ca33e10974..6c1f24942b 100644
--- a/dag/walk_test.go
+++ b/dag/walk_test.go
@@ -175,43 +175,42 @@ func TestWalker_removeVertex(t *testing.T) {
 }
 
 func TestWalker_newEdge(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))
+	var g AcyclicGraph
+	g.Add(1)
+	g.Add(2)
+	g.Connect(BasicEdge(1, 2))
 
-		// Record function
-		var order []interface{}
-		recordF := walkCbRecord(&order)
+	// Record function
+	var order []interface{}
+	recordF := walkCbRecord(&order)
 
-		// Build a callback that delays until we close a channel
-		var w *Walker
-		cb := func(v Vertex) error {
-			if v == 1 {
-				g.Add(3)
-				g.Connect(BasicEdge(3, 2))
-				w.Update(&g)
-			}
+	var w *Walker
+	cb := func(v Vertex) error {
+		// record where we are first, otherwise the Updated vertex may get
+		// walked before the first visit.
+		err := recordF(v)
 
-			return recordF(v)
+		if v == 1 {
+			g.Add(3)
+			g.Connect(BasicEdge(3, 2))
+			w.Update(&g)
 		}
+		return err
+	}
 
-		// Add the initial vertices
-		w = &Walker{Callback: cb}
-		w.Update(&g)
+	// Add the initial vertices
+	w = &Walker{Callback: cb}
+	w.Update(&g)
 
-		// Wait
-		if err := w.Wait(); err != nil {
-			t.Fatalf("err: %s", err)
-		}
+	// Wait
+	if err := w.Wait(); err != nil {
+		t.Fatalf("err: %s", err)
+	}
 
-		// Check
-		expected := []interface{}{1, 3, 2}
-		if !reflect.DeepEqual(order, expected) {
-			t.Fatalf("bad: %#v", order)
-		}
+	// Check
+	expected := []interface{}{1, 3, 2}
+	if !reflect.DeepEqual(order, expected) {
+		t.Fatalf("bad: %#v", order)
 	}
 }