From 7f98a8b7ca7e915f84e0905128ba97cd9bc9cf2d Mon Sep 17 00:00:00 2001
From: Marten Seemann <martenseemann@gmail.com>
Date: Mon, 25 Aug 2025 15:25:50 +0800
Subject: [PATCH] utils: use synctest to make the timer tests fully
 deterministic (#5306)

* utils: use synctest to make the timer tests fully deterministic

* Go 1.24 workaround
---
 internal/utils/timer_test.go | 178 ++++++++++++++++-------------------
 1 file changed, 83 insertions(+), 95 deletions(-)

diff --git a/internal/utils/timer_test.go b/internal/utils/timer_test.go
index 4d0742cc3..1a17cab15 100644
--- a/internal/utils/timer_test.go
+++ b/internal/utils/timer_test.go
@@ -4,97 +4,83 @@ import (
 	"testing"
 	"time"
 
+	"github.com/quic-go/quic-go/internal/synctest"
+
 	"github.com/stretchr/testify/require"
 )
 
-const testDuration = 10 * time.Millisecond
+func TestTimerResets(t *testing.T) {
+	synctest.Test(t, func(t *testing.T) {
+		timer := NewTimer()
 
-func TestTimerCreateAndReset(t *testing.T) {
-	timer := NewTimer()
-	select {
-	case <-timer.Chan():
-		t.Fatal("timer should not have fired")
-	default:
-	}
-
-	deadline := time.Now().Add(testDuration)
-	timer.Reset(deadline)
-	require.Equal(t, deadline, timer.Deadline())
-
-	select {
-	case <-timer.Chan():
-	case <-time.After(2 * testDuration):
-		t.Fatal("timer should have fired")
-	}
-
-	timer.SetRead()
-	timer.Reset(time.Now().Add(testDuration))
-
-	select {
-	case <-timer.Chan():
-	case <-time.After(2 * testDuration):
-		t.Fatal("timer should have fired")
-	}
-}
-
-func TestTimerMultipleResets(t *testing.T) {
-	timer := NewTimer()
-	for i := 0; i < 10; i++ {
-		timer.Reset(time.Now().Add(testDuration))
-		if i%2 == 0 {
-			select {
-			case <-timer.Chan():
-			case <-time.After(2 * testDuration):
-				t.Fatal("timer should have fired")
-			}
-			timer.SetRead()
-		} else {
-			time.Sleep(testDuration * 2)
+		select {
+		case <-timer.Chan():
+			t.Fatal("timer should not have fired")
+		default:
 		}
-	}
 
-	select {
-	case <-timer.Chan():
-	case <-time.After(2 * testDuration):
-		t.Fatal("timer should have fired")
-	}
+		start := time.Now()
+
+		// timer fires immediately for a deadline in the past
+		timer.Reset(time.Now().Add(-time.Second))
+		select {
+		case <-timer.Chan():
+			require.Zero(t, time.Since(start))
+			timer.SetRead()
+		case <-time.After(time.Hour): // this can be replaced with a default once we drop support for Go 1.24
+			t.Fatal("timer should have fired")
+		}
+
+		// timer reset without getting read
+		for range 10 {
+			time.Sleep(time.Second)
+			timer.Reset(time.Now().Add(time.Hour))
+		}
+		select {
+		case <-timer.Chan():
+			require.Equal(t, time.Since(start), time.Hour+10*time.Second)
+			timer.SetRead()
+		case <-time.After(2 * time.Hour):
+			t.Fatal("timer should have fired")
+		}
+
+		const d = 10 * time.Minute
+		for i := range 10 {
+			start := time.Now()
+			timer.Reset(time.Now().Add(d))
+			if i%2 == 0 {
+				select {
+				case <-timer.Chan():
+					require.Equal(t, time.Since(start), d)
+				case <-time.After(2 * d):
+					t.Fatal("timer should have fired")
+				}
+				timer.SetRead()
+			} else {
+				time.Sleep(2 * d)
+			}
+		}
+
+		select {
+		case <-timer.Chan():
+		default:
+			t.Fatal("timer should have fired")
+		}
+	})
 }
 
-func TestTimerResetWithoutExpiration(t *testing.T) {
-	timer := NewTimer()
-	for i := 0; i < 10; i++ {
-		timer.Reset(time.Now().Add(time.Hour))
-	}
-	timer.Reset(time.Now().Add(testDuration))
+func TestTimerClearDeadline(t *testing.T) {
+	synctest.Test(t, func(t *testing.T) {
+		timer := NewTimer()
+		timer.Reset(time.Time{})
 
-	select {
-	case <-timer.Chan():
-	case <-time.After(2 * testDuration):
-		t.Fatal("timer should have fired")
-	}
-}
-
-func TestTimerPastDeadline(t *testing.T) {
-	timer := NewTimer()
-	timer.Reset(time.Now().Add(-time.Second))
-
-	select {
-	case <-timer.Chan():
-	case <-time.After(testDuration):
-		t.Fatal("timer should have fired immediately")
-	}
-}
-
-func TestTimerZeroDeadline(t *testing.T) {
-	timer := NewTimer()
-	timer.Reset(time.Time{})
-
-	// we don't expect the timer to be set for a zero deadline
-	select {
-	case <-timer.Chan():
-		t.Fatal("timer should not have fired")
-	case <-time.After(testDuration):
-	}
+		// we don't expect the timer to be set for a zero deadline
+		select {
+		case <-timer.Chan():
+			t.Fatal("timer should not have fired")
+		case <-time.After(time.Hour):
+		}
+	})
 }
 
 func TestTimerSameDeadline(t *testing.T) {
@@ -105,7 +91,7 @@ func TestTimerSameDeadline(t *testing.T) {
 
 		select {
 		case <-timer.Chan():
-		case <-time.After(testDuration):
+		default:
 			t.Fatal("timer should have fired")
 		}
 
@@ -114,7 +100,7 @@ func TestTimerSameDeadline(t *testing.T) {
 
 		select {
 		case <-timer.Chan():
-		case <-time.After(testDuration):
+		default:
 			t.Fatal("timer should have fired")
 		}
 	})
@@ -126,26 +112,28 @@ func TestTimerSameDeadline(t *testing.T) {
 
 		select {
 		case <-timer.Chan():
-		case <-time.After(testDuration):
+		default:
 			t.Fatal("timer should have fired")
 		}
 
 		select {
 		case <-timer.Chan():
 			t.Fatal("timer should not have fired again")
-		case <-time.After(testDuration):
+		default:
 		}
 	})
 }
 
-func TestTimerStopping(t *testing.T) {
-	timer := NewTimer()
-	timer.Reset(time.Now().Add(testDuration))
-	timer.Stop()
+func TestTimerStop(t *testing.T) {
+	synctest.Test(t, func(t *testing.T) {
+		timer := NewTimer()
+		timer.Reset(time.Now().Add(time.Second))
+		timer.Stop()
 
-	select {
-	case <-timer.Chan():
-		t.Fatal("timer should not have fired")
-	case <-time.After(2 * testDuration):
-	}
+		select {
+		case <-timer.Chan():
+			t.Fatal("timer should not have fired")
+		case <-time.After(time.Hour):
+		}
+	})
 }