test(aggregator): cover the aggregator startup at epoch zero

Check that `inform_epoch` and the epoch settings discrepancy handling
succeed at epoch zero with a clamped signer retrieval epoch.

Author: jpraynaud

mithril-aggregator/src/services/epoch_service.rs

@@ -954,7 +954,7 @@ mod tests {
 
         async fn build(self) -> MithrilEpochService {
             let signer_retrieval_epoch =
-                self.current_epoch.offset_to_signer_retrieval_epoch().unwrap();
+                self.current_epoch.offset_to_signer_retrieval_epoch_saturating();
             let next_signer_retrieval_epoch =
                 self.current_epoch.offset_to_next_signer_retrieval_epoch();
 
@@ -1095,6 +1095,29 @@ mod tests {
         );
     }
 
+    #[tokio::test]
+    async fn inform_epoch_at_epoch_zero_retrieves_signers_at_epoch_zero() {
+        let epoch = Epoch(0);
+        let epoch_fixture = MithrilFixtureBuilder::default().with_signers(3).build();
+
+        let mut service = EpochServiceBuilder::new(epoch, epoch_fixture.clone()).build().await;
+
+        service
+            .inform_epoch(epoch)
+            .await
+            .expect("inform_epoch should not fail at epoch zero");
+
+        assert_eq!(epoch, service.epoch_of_current_data().unwrap());
+        assert_eq!(
+            epoch_fixture.signers(),
+            service.current_signers().unwrap().clone()
+        );
+        assert_eq!(
+            epoch_fixture.signers(),
+            service.next_signers().unwrap().clone()
+        );
+    }
+
     #[tokio::test]
     async fn inform_epoch_get_signed_entity_config_from_its_dependencies_and_store() {
         let epoch = Epoch(5);

mithril-aggregator/src/store/epoch_settings_storer.rs

@@ -244,4 +244,43 @@ mod tests {
         let epoch_settings_stored = store.get_epoch_settings(epoch + 2).await.unwrap();
         assert!(epoch_settings_stored.is_none());
     }
+
+    #[tokio::test]
+    async fn test_handle_discrepancies_at_startup_at_epoch_zero_clamps_the_aggregation_epoch() {
+        let epoch_settings = AggregatorEpochSettings::dummy();
+        let mut aggregation_epoch_settings = epoch_settings.clone();
+        aggregation_epoch_settings.protocol_parameters.k += 15;
+
+        let mut next_aggregation_epoch_settings = epoch_settings.clone();
+        next_aggregation_epoch_settings.protocol_parameters.k += 26;
+
+        let mut registration_epoch_settings = epoch_settings.clone();
+        registration_epoch_settings.protocol_parameters.k += 37;
+
+        let epoch = Epoch(0);
+        let store = FakeEpochSettingsStorer::new(vec![]);
+        store
+            .handle_discrepancies_at_startup(&MithrilNetworkConfiguration {
+                epoch,
+                configuration_for_aggregation: aggregation_epoch_settings
+                    .clone()
+                    .into_network_configuration_for_epoch(BTreeSet::new()),
+                configuration_for_next_aggregation: next_aggregation_epoch_settings
+                    .into_network_configuration_for_epoch(BTreeSet::new()),
+                configuration_for_registration: registration_epoch_settings
+                    .clone()
+                    .into_network_configuration_for_epoch(BTreeSet::new()),
+            })
+            .await
+            .unwrap();
+
+        let epoch_settings_stored = store.get_epoch_settings(Epoch(0)).await.unwrap();
+        assert_eq!(Some(aggregation_epoch_settings), epoch_settings_stored);
+
+        let epoch_settings_stored = store.get_epoch_settings(Epoch(1)).await.unwrap();
+        assert_eq!(Some(registration_epoch_settings), epoch_settings_stored);
+
+        let epoch_settings_stored = store.get_epoch_settings(Epoch(2)).await.unwrap();
+        assert!(epoch_settings_stored.is_none());
+    }
 }