make the repair_backoff test more robust (#1095)

* more the repair_backoff test more robust

* fix names and magic numbers

src/window.rs

@@ -1056,23 +1056,30 @@ mod test {
  }
  #[test]
  pub fn test_repair_backoff() {
- let mut last = 0;
- let mut times = 0;
- let total: usize = (0..127)
- .map(|x| {
- let rv = repair_backoff(&mut last, &mut times, 1) as usize;
- assert_eq!(times, x + 2);
- rv
+ let num_tests = 100;
+ let res: usize = (0..num_tests)
+ .map(|_| {
+ let mut last = 0;
+ let mut times = 0;
+ let total: usize = (0..127)
+ .map(|x| {
+ let rv = repair_backoff(&mut last, &mut times, 1) as usize;
+ assert_eq!(times, x + 2);
+ rv
+ })
+ .sum();
+ assert_eq!(times, 128);
+ assert_eq!(last, 1);
+ repair_backoff(&mut last, &mut times, 1);
+ assert_eq!(times, 64);
+ repair_backoff(&mut last, &mut times, 2);
+ assert_eq!(times, 2);
+ assert_eq!(last, 2);
+ total
  })
  .sum();
- assert_eq!(times, 128);
- assert_eq!(last, 1);
- assert!(total > 0);
- assert!(total < 127);
- repair_backoff(&mut last, &mut times, 1);
- assert_eq!(times, 64);
- repair_backoff(&mut last, &mut times, 2);
- assert_eq!(times, 2);
- assert_eq!(last, 2);
+ let avg = res / num_tests;
+ assert!(avg >= 3);
+ assert!(avg <= 5);
  }
 }