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Fix removeEdge test failures

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The removeEdge test could fail intermittently with the wrong order.

The precondition of a 1->2->3 order wasn't met, because there was no
edge from 1->3, so 3->1->2 was also a valid ordering.

The other failure was a bookkeeping error, were the recorded order may
not match the visited order. What happened in this case was the gateCh
was closed by V2, allowing V3 to run which could beat V2 to recording
its visit. Now the visit is recorded as part of the vertex walk, and the
gate is released as the final operation.

The order is deterministic now, so remove the brute-force test loop.
This commit is contained in:
James Bardin 2017-02-20 15:36:15 -05:00
parent d01b0b0647
commit bfa6ab4617
1 changed files with 50 additions and 50 deletions
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100
dag/walk_test.go
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@ -215,63 +215,63 @@ func TestWalker_newEdge(t *testing.T) {
} }
func TestWalker_removeEdge(t *testing.T) { func TestWalker_removeEdge(t *testing.T) {
// Run it a bunch of times since it is timing dependent var g AcyclicGraph
for i := 0; i < 50; i++ { g.Add(1)
var g AcyclicGraph g.Add(2)
g.Add(1) g.Add(3)
g.Add(2) g.Connect(BasicEdge(1, 2))
g.Add(3) g.Connect(BasicEdge(1, 3))
g.Connect(BasicEdge(1, 2)) g.Connect(BasicEdge(3, 2))
g.Connect(BasicEdge(3, 2))
// Record function // Record function
var order []interface{} var order []interface{}
recordF := walkCbRecord(&order) recordF := walkCbRecord(&order)
// The way this works is that our original graph forces // The way this works is that our original graph forces
// the order of 1 => 3 => 2. During the execution of 1, we // the order of 1 => 3 => 2. During the execution of 1, we
// remove the edge forcing 3 before 2. Then, during the execution // remove the edge forcing 3 before 2. Then, during the execution
// of 3, we wait on a channel that is only closed by 2, implicitly // of 3, we wait on a channel that is only closed by 2, implicitly
// forcing 2 before 3 via the callback (and not the graph). If // forcing 2 before 3 via the callback (and not the graph). If
// 2 cannot execute before 3 (edge removal is non-functional), then // 2 cannot execute before 3 (edge removal is non-functional), then
// this test will timeout. // this test will timeout.
var w *Walker var w *Walker
gateCh := make(chan struct{}) gateCh := make(chan struct{})
cb := func(v Vertex) error { cb := func(v Vertex) error {
if v == 1 { switch v {
g.RemoveEdge(BasicEdge(3, 2)) case 1:
w.Update(&g) g.RemoveEdge(BasicEdge(3, 2))
w.Update(&g)
case 2:
// this visit isn't completed until we've recorded it
// Once the visit is official, we can then close the gate to
// let 3 continue.
defer close(gateCh)
case 3:
select {
case <-gateCh:
case <-time.After(50 * time.Millisecond):
return fmt.Errorf("timeout 3 waiting for 2")
} }
if v == 2 {
close(gateCh)
}
if v == 3 {
select {
case <-gateCh:
case <-time.After(50 * time.Millisecond):
return fmt.Errorf("timeout 3 waiting for 2")
}
}
return recordF(v)
} }
// Add the initial vertices return recordF(v)
w = &Walker{Callback: cb} }
w.Update(&g)
// Wait // Add the initial vertices
if err := w.Wait(); err != nil { w = &Walker{Callback: cb}
t.Fatalf("err: %s", err) w.Update(&g)
}
// Check // Wait
expected := []interface{}{1, 2, 3} if err := w.Wait(); err != nil {
if !reflect.DeepEqual(order, expected) { t.Fatalf("err: %s", err)
t.Fatalf("bad: %#v", order) }
}
// Check
expected := []interface{}{1, 2, 3}
if !reflect.DeepEqual(order, expected) {
t.Fatalf("bad: %#v", order)
} }
} }