fix flaky TTL test

Author: marten-seemann

client.go

@@ -26,6 +26,8 @@ const (
 	IPv4AndIPv6        = IPv4 | IPv6 // default option
 )
 
+var initialQueryInterval = 4 * time.Second
+
 // Client structure encapsulates both IPv4/IPv6 UDP connections.
 type client struct {
 	ipv4conn *ipv4.PacketConn
@@ -371,7 +373,7 @@ func (c *client) periodicQuery(ctx context.Context, params *lookupParams) error
 	}
 
 	const maxInterval = 60 * time.Second
-	interval := 4 * time.Second
+	interval := initialQueryInterval
 	timer := time.NewTimer(interval)
 	defer timer.Stop()
 	for {

service_test.go

@@ -143,11 +143,14 @@ func TestSubtype(t *testing.T) {
 	t.Run("ttl", func(t *testing.T) {
 		origTTL := defaultTTL
 		origCleanupFreq := cleanupFreq
-		defer func() {
+		origInitialQueryInterval := initialQueryInterval
+		t.Cleanup(func() {
 			defaultTTL = origTTL
 			cleanupFreq = origCleanupFreq
-		}()
-		defaultTTL = 2 // 2 seconds
+			initialQueryInterval = origInitialQueryInterval
+		})
+		defaultTTL = 1 // 1 second
+		initialQueryInterval = 100 * time.Millisecond
 		cleanupFreq = 100 * time.Millisecond
 
 		ctx, cancel := context.WithTimeout(context.Background(), 5*time.Second)
@@ -160,8 +163,8 @@ func TestSubtype(t *testing.T) {
 		}
 
 		<-ctx.Done()
-		if len(entries) != 2 {
-			t.Fatalf("Expected to have received 2 entries, but got %d", len(entries))
+		if len(entries) < 2 {
+			t.Fatalf("Expected to have received at least 2 entries, but got %d", len(entries))
 		}
 		res1 := <-entries
 		res2 := <-entries