scheduler: Fix `many` with non-zero seed (#50482)

Agus Zubiaga created 1 month ago

The iteration range was `(seed..num_iterations)`, which produces an
empty range whenever `seed >= num_iterations`. Changed it to
`(seed..seed + num_iterations)` so the range always runs the correct
number of iterations starting from the given seed.

Release Notes:

- N/A

Change summary

crates/scheduler/src/test_scheduler.rs |  2 +-
crates/scheduler/src/tests.rs          | 25 +++++++++++++++++++++++++
2 files changed, 26 insertions(+), 1 deletion(-)

Detailed changes

crates/scheduler/src/test_scheduler.rs

@@ -57,7 +57,7 @@ impl TestScheduler {
             .map(|seed| seed.parse().unwrap())
             .unwrap_or(0);
 
-        (seed..num_iterations as u64)
+        (seed..seed + num_iterations as u64)
             .map(|seed| {
                 let mut unwind_safe_f = AssertUnwindSafe(&mut f);
                 eprintln!("Running seed: {seed}");

crates/scheduler/src/tests.rs

@@ -290,6 +290,31 @@ fn test_helper_methods() {
     assert_eq!(results, vec![10, 10, 10]);
 }
 
+#[test]
+fn test_many_with_arbitrary_seed() {
+    for seed in [0u64, 1, 5, 42] {
+        let mut seeds_seen = Vec::new();
+        let iterations = 3usize;
+
+        for current_seed in seed..seed + iterations as u64 {
+            let scheduler = Arc::new(TestScheduler::new(TestSchedulerConfig::with_seed(
+                current_seed,
+            )));
+            let captured_seed = current_seed;
+            scheduler
+                .foreground()
+                .block_on(async { seeds_seen.push(captured_seed) });
+            scheduler.run();
+        }
+
+        assert_eq!(
+            seeds_seen,
+            (seed..seed + iterations as u64).collect::<Vec<_>>(),
+            "Expected {iterations} iterations starting at seed {seed}"
+        );
+    }
+}
+
 #[test]
 fn test_block_with_timeout() {
     // Test case: future completes within timeout