cmd/go: deflake TestGoTestJSON further

Even after disabling on 1-CPU systems, builders are still flaking too often.
Unless there are at least 4 CPUs, don't require test interlacing at all.

Fixes #22665 (again).

Change-Id: Ief792c496c1ee70939532e6ca8bef012fe78178e
Reviewed-on: https://go-review.googlesource.com/77310
Run-TryBot: Russ Cox <rsc@golang.org>
Reviewed-by: Russ Cox <rsc@golang.org>

diff --git a/src/cmd/go/go_test.go b/src/cmd/go/go_test.go
index fa3ca530d1bf52e97e7e674a793abc8629c42738..2cf3d7d9de8dc2c48db621bd781292754dab9978 100644 (file)
--- a/src/cmd/go/go_test.go
+++ b/src/cmd/go/go_test.go
@@ -5119,9 +5119,6 @@ func TestGoTestMinusN(t *testing.T) {
 }
 
 func TestGoTestJSON(t *testing.T) {
-       if runtime.NumCPU() == 1 {
-               t.Skip("skipping on uniprocessor")
-       }
        tg := testgo(t)
        defer tg.cleanup()
        tg.parallel()
@@ -5130,32 +5127,42 @@ func TestGoTestJSON(t *testing.T) {
        tg.setenv("GOPATH", filepath.Join(tg.pwd(), "testdata"))
 
        // Test that math and fmt output is interlaced.
-       if runtime.GOMAXPROCS(-1) < 2 {
-               tg.setenv("GOMAXPROCS", "2")
-       }
-       // This has the potential to be a flaky test.
-       // Probably the first try will work, but the second try should have
-       // both tests equally cached and should definitely work.
+       // This has the potential to be a flaky test,
+       // especially on uniprocessor systems, so only
+       // require interlacing if we have at least 4 CPUs.
+       // We also try twice, hoping that the cache will be
+       // warmed up the second time.
+       needInterlace := runtime.GOMAXPROCS(-1) >= 4
        for try := 0; ; try++ {
                tg.run("test", "-json", "-short", "-v", "sleepy1", "sleepy2")
+               sawSleepy1 := false
+               sawSleepy2 := false
                state := 0
                for _, line := range strings.Split(tg.getStdout(), "\n") {
-                       if state == 0 && strings.Contains(line, `"Package":"sleepy1"`) {
-                               state = 1
+                       if strings.Contains(line, `"Package":"sleepy1"`) {
+                               sawSleepy1 = true
+                               if state == 0 {
+                                       state = 1
+                               }
+                               if state == 2 {
+                                       state = 3
+                               }
                        }
-                       if state == 1 && strings.Contains(line, `"Package":"sleepy2"`) {
-                               state = 2
-                       }
-                       if state == 2 && strings.Contains(line, `"Package":"sleepy1"`) {
-                               state = 3
-                               break
+                       if strings.Contains(line, `"Package":"sleepy2"`) {
+                               sawSleepy2 = true
+                               if state == 1 {
+                                       state = 2
+                               }
                        }
                }
-               if state != 3 {
+               if !sawSleepy1 || !sawSleepy2 {
+                       t.Fatalf("did not see output from both sleepy1 and sleepy2")
+               }
+               if needInterlace && state != 3 {
                        if try < 1 {
                                continue
                        }
-                       t.Fatalf("did not find fmt interlaced with math")
+                       t.Fatalf("did not find sleepy1 interlaced with sleepy2")
                }
                break
        }