rotate collators based on session index and collators size

integration-tests/src/kusama_test_net.rs

@@ -307,6 +307,10 @@ pub mod basilisk {
 				get_account_id_from_seed::<sr25519::Public>("Bob"),
 				get_from_seed::<AuraId>("Bob"),
 			),
+			(
+				get_account_id_from_seed::<sr25519::Public>("Charlie"),
+				get_from_seed::<AuraId>("Charlie"),
+			),
 		]
 	}
 

integration-tests/src/lib.rs

@@ -10,6 +10,7 @@ mod nft_marketplace;
 mod non_native_fee;
 mod oracle;
 mod router;
+mod sessions;
 mod transact_call_filter;
 mod vesting;
 mod xyk;

integration-tests/src/sessions.rs

@@ -0,0 +1,53 @@
+#![cfg(test)]
+use crate::kusama_test_net::*;
+use basilisk_runtime::CollatorRewards;
+use basilisk_runtime::Runtime;
+use frame_support::traits::Contains;
+use pallet_session::SessionManager;
+use polkadot_xcm::v3::prelude::*;
+use polkadot_xcm::VersionedXcm;
+use xcm_emulator::TestExt;
+
+#[test]
+fn new_session_should_rotate_collators_list() {
+	TestNet::reset();
+
+	Basilisk::execute_with(|| {
+		let collator1 = basilisk::invulnerables()[0].0.clone(); //d435...
+		let collator2 = basilisk::invulnerables()[1].0.clone(); //8eaf...
+		let collator3 = basilisk::invulnerables()[2].0.clone(); //90b5...
+
+		let collators = CollatorRewards::new_session(0).unwrap();
+		assert_eq!(collators, vec![collator2.clone(), collator3.clone(), collator1.clone()]);
+
+		let collators = CollatorRewards::new_session(1).unwrap();
+		assert_eq!(collators, vec![collator2.clone(), collator3.clone(), collator1.clone()]);
+
+		let collators = CollatorRewards::new_session(2).unwrap();
+		assert_eq!(collators, vec![collator2.clone(), collator3.clone(), collator1.clone()]);
+
+		let collators = CollatorRewards::new_session(3).unwrap();
+		assert_eq!(collators, vec![collator3.clone(), collator1.clone(), collator2.clone()]);
+
+		let collators = CollatorRewards::new_session(4).unwrap();
+		assert_eq!(collators, vec![collator3.clone(), collator1.clone(), collator2.clone()]);
+
+		let collators = CollatorRewards::new_session(5).unwrap();
+		assert_eq!(collators, vec![collator3.clone(), collator1.clone(), collator2.clone()]);
+
+		let collators = CollatorRewards::new_session(6).unwrap();
+		assert_eq!(collators, vec![collator1.clone(), collator2.clone(), collator3.clone()]);
+
+		let collators = CollatorRewards::new_session(7).unwrap();
+		assert_eq!(collators, vec![collator1.clone(), collator2.clone(), collator3.clone()]);
+
+		let collators = CollatorRewards::new_session(8).unwrap();
+		assert_eq!(collators, vec![collator1.clone(), collator2.clone(), collator3.clone()]);
+
+		let collators = CollatorRewards::new_session(9).unwrap();
+		assert_eq!(collators, vec![collator2.clone(), collator3.clone(), collator1.clone()]);
+
+		let collators = CollatorRewards::new_session(10).unwrap();
+		assert_eq!(collators, vec![collator2.clone(), collator3.clone(), collator1.clone()]);
+	});
+}

runtime/basilisk/src/system.rs

@@ -17,7 +17,6 @@
 
 use super::*;
 use crate::governance::{origins::GeneralAdmin, TechCommitteeMajority, TechnicalCollective, TreasuryAccount};
-use sp_io::transaction_index::index;
 
 use pallet_transaction_multi_payment::{DepositAll, TransferFees};
 use pallet_transaction_payment::{Multiplier, TargetedFeeAdjustment};
@@ -551,11 +550,10 @@ impl SessionManager<AccountId> for RotatingCollatorManager {
 		// We wrap the ` SessionManager` implementation of `CollatorSelection` to get the collators that
 		// we hand out rewards to,
 		// then we rotate the collators to have a regular distribution for block production
-
 		let mut collators = CollatorSelection::new_session(new_index)?;
 
-		if !collators.is_empty() {
-			collators.rotate_left(1);
+		if let Some(amount) = (new_index as usize).checked_div(collators.len()) {
+			collators.rotate_left(amount);
 		}
 
 		Some(collators)