net/http: run TestServerShutdownStateNew in a synctest bubble

Took ~12s previously, ~0s now.

Change-Id: I72580fbde73482a40142cf84cd3d78a50afb9f44
Reviewed-on: https://go-review.googlesource.com/c/go/+/630382
LUCI-TryBot-Result: Go LUCI <golang-scoped@luci-project-accounts.iam.gserviceaccount.com>
Reviewed-by: Jonathan Amsterdam <jba@google.com>

1 files changed, 32 insertions, 0 deletions

diff --git a/src/net/http/clientserver_test.go b/src/net/http/clientserver_test.go
index 606715a25c..0873038757 100644
--- a/src/net/http/clientserver_test.go
+++ b/src/net/http/clientserver_test.go
@@ -15,6 +15,7 @@ import (
 	"crypto/tls"
 	"fmt"
 	"hash"
+	"internal/synctest"
 	"io"
 	"log"
 	"maps"
@@ -93,6 +94,37 @@ func run[T TBRun[T]](t T, f func(t T, mode testMode), opts ...any) {
 	}
 }
 
+// cleanupT wraps a testing.T and adds its own Cleanup method.
+// Used to execute cleanup functions within a synctest bubble.
+type cleanupT struct {
+	*testing.T
+	cleanups []func()
+}
+
+// Cleanup replaces T.Cleanup.
+func (t *cleanupT) Cleanup(f func()) {
+	t.cleanups = append(t.cleanups, f)
+}
+
+func (t *cleanupT) done() {
+	for _, f := range slices.Backward(t.cleanups) {
+		f()
+	}
+}
+
+// runSynctest is run combined with synctest.Run.
+//
+// The TB passed to f arranges for cleanup functions to be run in the synctest bubble.
+func runSynctest(t *testing.T, f func(t testing.TB, mode testMode), opts ...any) {
+	run(t, func(t *testing.T, mode testMode) {
+		synctest.Run(func() {
+			ct := &cleanupT{T: t}
+			defer ct.done()
+			f(ct, mode)
+		})
+	}, opts...)
+}
+
 type clientServerTest struct {
 	t  testing.TB
 	h2 bool