test: unclaimed UDs out of UD reeval window

pallets/universal-dividend/src/compute_claim_uds.rs

@@ -109,4 +109,19 @@ mod tests {
             (2, 110_000)
         );
     }
+
+    #[test]
+    fn very_old_unclaimed_ud_out_of_reevals() {
+        let past_reevals = vec![
+            // (3, 100 as Balance), "old" reeval which has gone out of reevals window.
+            (4, 1_000 as Balance),
+            (5, 10_000 as Balance),
+            (6, 100_000 as Balance),
+        ];
+        // All the UDs out of the reeval window must produce 0 money units
+        assert_eq!(
+            compute_claim_uds(7, 1, past_reevals.into_iter()),
+            (3, 111_000)
+        );
+    }
 }