Add all mismatches in chronological order to MismatchedChecksum error

src/error.rs

@@ -21,7 +21,9 @@ pub enum GgrsError {
     /// [`SyncTestSession`]: crate::SyncTestSession
     MismatchedChecksum {
         /// The frame at which the mismatch occurred.
-        frame: Frame,
+        current_frame: Frame,
+        /// The frames with mismatched checksums (one or more)
+        mismatched_frames: Vec<Frame>,
     },
     /// The Session is not synchronized yet. Please start the session and wait a few ms to let the clients synchronize.
     NotSynchronized,
@@ -47,11 +49,14 @@ impl Display for GgrsError {
                     "The session is not yet synchronized with all remote sessions."
                 )
             }
-            GgrsError::MismatchedChecksum { frame } => {
+            GgrsError::MismatchedChecksum {
+                current_frame,
+                mismatched_frames,
+            } => {
                 write!(
                     f,
-                    "Detected checksum mismatch during rollback on frame {}.",
-                    frame
+                    "Detected checksum mismatch during rollback on frame {}, mismatched frames: {:?}",
+                    current_frame, mismatched_frames
                 )
             }
             GgrsError::SpectatorTooFarBehind => {

src/sessions/sync_test_session.rs

@@ -90,12 +90,15 @@ impl<T: Config> SyncTestSession<T> {
         if self.check_distance > 0 && current_frame > self.check_distance as i32 {
             // compare checksums of older frames to our checksum history (where only the first version of any checksum is recorded)
             let oldest_frame_to_check = current_frame - self.check_distance as Frame;
-            for frame_to_check in oldest_frame_to_check..=current_frame {
-                if !self.checksums_consistent(frame_to_check) {
-                    return Err(GgrsError::MismatchedChecksum {
-                        frame: frame_to_check,
-                    });
-                }
+            let mismatched_frames: Vec<_> = (oldest_frame_to_check..=current_frame)
+                .filter(|frame_to_check| !self.checksums_consistent(*frame_to_check))
+                .collect();
+
+            if !mismatched_frames.is_empty() {
+                return Err(GgrsError::MismatchedChecksum {
+                    current_frame,
+                    mismatched_frames,
+                });
             }
 
             // simulate rollbacks according to the check_distance