metrics: make flawed test less flawed (ethereum#20818)

metrics/timer_test.go

@@ -45,10 +45,23 @@ func TestTimerStop(t *testing.T) {
 }
 
 func TestTimerFunc(t *testing.T) {
-	tm := NewTimer()
-	tm.Time(func() { time.Sleep(50e6) })
-	if max := tm.Max(); 35e6 > max || max > 95e6 {
-		t.Errorf("tm.Max(): 35e6 > %v || %v > 95e6\n", max, max)
+	var (
+		tm         = NewTimer()
+		testStart  = time.Now()
+		actualTime time.Duration
+	)
+	tm.Time(func() {
+		time.Sleep(50 * time.Millisecond)
+		actualTime = time.Since(testStart)
+	})
+	var (
+		drift    = time.Millisecond * 2
+		measured = time.Duration(tm.Max())
+		ceil     = actualTime + drift
+		floor    = actualTime - drift
+	)
+	if measured > ceil || measured < floor {
+		t.Errorf("tm.Max(): %v > %v || %v > %v\n", measured, ceil, measured, floor)
 	}
 }