From 0020076f2b2c79edd5b16495dc6ec0ba84d93965 Mon Sep 17 00:00:00 2001
From: Joachim Bauch <bauch@struktur.de>
Date: Tue, 17 Jan 2023 14:51:02 +0100
Subject: [PATCH] Run function to test for goroutine leaks as subtest.

This makes sure the test has been completely teared down before the
goroutines are counted and thus should prevent flaky failed tests.
---
 natsclient_loopback_test.go |  8 ++++----
 natsclient_test.go          |  8 ++++----
 testutils_test.go           | 25 ++++++++++++++++++++++---
 3 files changed, 30 insertions(+), 11 deletions(-)

diff --git a/natsclient_loopback_test.go b/natsclient_loopback_test.go
index 3cb35b1..ff8994c 100644
--- a/natsclient_loopback_test.go
+++ b/natsclient_loopback_test.go
@@ -60,7 +60,7 @@ func CreateLoopbackNatsClientForTest(t *testing.T) NatsClient {
 }
 
 func TestLoopbackNatsClient_Subscribe(t *testing.T) {
-	ensureNoGoroutinesLeak(t, func() {
+	ensureNoGoroutinesLeak(t, func(t *testing.T) {
 		client := CreateLoopbackNatsClientForTest(t)
 
 		testNatsClient_Subscribe(t, client)
@@ -68,7 +68,7 @@ func TestLoopbackNatsClient_Subscribe(t *testing.T) {
 }
 
 func TestLoopbackClient_PublishAfterClose(t *testing.T) {
-	ensureNoGoroutinesLeak(t, func() {
+	ensureNoGoroutinesLeak(t, func(t *testing.T) {
 		client := CreateLoopbackNatsClientForTest(t)
 
 		testNatsClient_PublishAfterClose(t, client)
@@ -76,7 +76,7 @@ func TestLoopbackClient_PublishAfterClose(t *testing.T) {
 }
 
 func TestLoopbackClient_SubscribeAfterClose(t *testing.T) {
-	ensureNoGoroutinesLeak(t, func() {
+	ensureNoGoroutinesLeak(t, func(t *testing.T) {
 		client := CreateLoopbackNatsClientForTest(t)
 
 		testNatsClient_SubscribeAfterClose(t, client)
@@ -84,7 +84,7 @@ func TestLoopbackClient_SubscribeAfterClose(t *testing.T) {
 }
 
 func TestLoopbackClient_BadSubjects(t *testing.T) {
-	ensureNoGoroutinesLeak(t, func() {
+	ensureNoGoroutinesLeak(t, func(t *testing.T) {
 		client := CreateLoopbackNatsClientForTest(t)
 
 		testNatsClient_BadSubjects(t, client)
diff --git a/natsclient_test.go b/natsclient_test.go
index 62defca..b72d291 100644
--- a/natsclient_test.go
+++ b/natsclient_test.go
@@ -105,7 +105,7 @@ func testNatsClient_Subscribe(t *testing.T, client NatsClient) {
 }
 
 func TestNatsClient_Subscribe(t *testing.T) {
-	ensureNoGoroutinesLeak(t, func() {
+	ensureNoGoroutinesLeak(t, func(t *testing.T) {
 		client := CreateLocalNatsClientForTest(t)
 
 		testNatsClient_Subscribe(t, client)
@@ -121,7 +121,7 @@ func testNatsClient_PublishAfterClose(t *testing.T, client NatsClient) {
 }
 
 func TestNatsClient_PublishAfterClose(t *testing.T) {
-	ensureNoGoroutinesLeak(t, func() {
+	ensureNoGoroutinesLeak(t, func(t *testing.T) {
 		client := CreateLocalNatsClientForTest(t)
 
 		testNatsClient_PublishAfterClose(t, client)
@@ -138,7 +138,7 @@ func testNatsClient_SubscribeAfterClose(t *testing.T, client NatsClient) {
 }
 
 func TestNatsClient_SubscribeAfterClose(t *testing.T) {
-	ensureNoGoroutinesLeak(t, func() {
+	ensureNoGoroutinesLeak(t, func(t *testing.T) {
 		client := CreateLocalNatsClientForTest(t)
 
 		testNatsClient_SubscribeAfterClose(t, client)
@@ -160,7 +160,7 @@ func testNatsClient_BadSubjects(t *testing.T, client NatsClient) {
 }
 
 func TestNatsClient_BadSubjects(t *testing.T) {
-	ensureNoGoroutinesLeak(t, func() {
+	ensureNoGoroutinesLeak(t, func(t *testing.T) {
 		client := CreateLocalNatsClientForTest(t)
 
 		testNatsClient_BadSubjects(t, client)
diff --git a/testutils_test.go b/testutils_test.go
index b789a2d..bcc781f 100644
--- a/testutils_test.go
+++ b/testutils_test.go
@@ -23,19 +23,38 @@ package signaling
 
 import (
 	"os"
+	"os/signal"
 	"runtime/pprof"
+	"sync"
 	"testing"
 	"time"
 )
 
-func ensureNoGoroutinesLeak(t *testing.T, f func()) {
+var listenSignalOnce sync.Once
+
+func ensureNoGoroutinesLeak(t *testing.T, f func(t *testing.T)) {
+	t.Helper()
+
+	// The signal package will start a goroutine the first time "signal.Notify"
+	// is called. Do so outside the function under test so the signal goroutine
+	// will not be shown as "leaking".
+	listenSignalOnce.Do(func() {
+		ch := make(chan os.Signal, 1)
+		signal.Notify(ch, os.Interrupt)
+		go func() {
+			for {
+				<-ch
+			}
+		}()
+	})
+
 	profile := pprof.Lookup("goroutine")
 	// Give time for things to settle before capturing the number of
 	// go routines
 	time.Sleep(500 * time.Millisecond)
 	before := profile.Count()
 
-	f()
+	t.Run("leakcheck", f)
 
 	var after int
 	// Give time for things to settle before capturing the number of
@@ -50,6 +69,6 @@ func ensureNoGoroutinesLeak(t *testing.T, f func()) {
 
 	if after != before {
 		profile.WriteTo(os.Stderr, 2) // nolint
-		t.Fatalf("Number of Go routines has changed in %s from %d to %d", t.Name(), before, after)
+		t.Fatalf("Number of Go routines has changed from %d to %d", before, after)
 	}
 }