add epoch retention tests

1 files changed, 29 insertions, 0 deletions

diff --git a/src/remake/records.rs b/src/remake/records.rs
index 84286f3..720aea1 100644
--- a/src/remake/records.rs
+++ b/src/remake/records.rs
@@ -531,6 +531,35 @@ mod tests {
         assert!(!none.covers(0, 0));
     }
 
+    /// Over random limits and ages: covered exactly while some given limit holds, and
+    /// what is covered stays covered when it is younger in either measure.
+    #[test]
+    fn retention_covers_while_a_limit_holds() {
+        crate::testrand::for_seeds(500, |rng| {
+            let limit =
+                |rng: &mut crate::testrand::Rng| rng.chance(0.7).then(|| rng.below(10) as u64);
+            let retention = Retention {
+                epochs: limit(rng),
+                age_ms: limit(rng).map(|ms| ms * 1_000),
+            };
+            let (epochs, age_ms) = (rng.below(12) as u64, rng.below(12_000) as u64);
+            let covered = retention.covers(epochs, age_ms);
+            let holds = retention.epochs.is_some_and(|limit| epochs <= limit)
+                || retention.age_ms.is_some_and(|limit| age_ms <= limit);
+            assert_eq!(
+                covered, holds,
+                "{retention:?} at {epochs} epochs, {age_ms} ms"
+            );
+            if covered {
+                let younger = (
+                    rng.below(epochs as usize + 1) as u64,
+                    rng.below(age_ms as usize + 1) as u64,
+                );
+                assert!(retention.covers(younger.0, younger.1));
+            }
+        });
+    }
+
     fn proposal(settle_until: u64) -> Proposal {
         Proposal {
             coordinator: "node-a".into(),