yamltests, beacon: port back crosslinks and pass all crosslinks test

beacon/src/executive/transition/per_epoch/crosslink.rs

+use crate::{Config, BeaconState, Error};
+
+impl<C: Config> BeaconState<C> {
+	/// Update crosslinks
+	pub fn process_crosslinks(&mut self) -> Result<(), Error> {
+		self.previous_crosslinks = self.current_crosslinks.clone();
+		for epoch in &[self.previous_epoch(), self.current_epoch()] {
+			for offset in 0..self.committee_count(*epoch) {
+				let shard = (self.start_shard(*epoch)? + offset) % C::shard_count();
+				let crosslink_committee = self.crosslink_committee(*epoch, shard)?;
+				let (winning_crosslink, attesting_indices) =
+					self.winning_crosslink_and_attesting_indices(*epoch, shard)?;
+				if 3 * self.total_balance(&attesting_indices) >=
+					2 * self.total_balance(&crosslink_committee)
+				{
+					self.current_crosslinks[shard as usize] = winning_crosslink;
+				}
+			}
+		}
+
+		Ok(())
+	}
+}

beacon/src/executive/transition/per_epoch/mod.rs

 mod helpers;
 mod justification;
+mod crosslink;

yamltests/transitiontests/src/epoch_processing.rs

@@ -18,21 +18,21 @@ impl<C: Config> Test for JustificationAndFinalizationTest<C> {
 	}
 }
 
-// #[derive(Serialize, Deserialize, Debug)]
-// #[serde(deny_unknown_fields)]
-// pub struct CrosslinksTest {
-// 	pub description: String,
-// 	pub pre: BeaconState,
-// 	pub post: Option<BeaconState>,
-// }
+#[derive(Serialize, Deserialize, Debug)]
+#[serde(deny_unknown_fields)]
+pub struct CrosslinksTest<C: Config> {
+	pub description: String,
+	pub pre: BeaconState<C>,
+	pub post: Option<BeaconState<C>>,
+}
 
-// impl Test for CrosslinksTest {
-// 	fn run<C: Config>(&self, config: &C) {
-// 		run_test_with(&self.description, &self.pre, self.post.as_ref(), config, |executive| {
-// 			executive.process_crosslinks()
-// 		});
-// 	}
-// }
+impl<C: Config> Test for CrosslinksTest<C> {
+	fn run(&self) {
+		run_test_with(&self.description, &self.pre, self.post.as_ref(), |state| {
+			state.process_crosslinks()
+		});
+	}
+}
 
 // #[derive(Serialize, Deserialize, Debug)]
 // #[serde(deny_unknown_fields)]

yamltests/transitiontests/src/main.rs

@@ -46,7 +46,7 @@ fn run_all<C: Config + serde::Serialize + DeserializeOwned>(runner: &str, file:
 		"transfer" => run::<TransferTest<C>>(file),
 		"voluntary_exit" => run::<VoluntaryExitTest<C>>(file),
 		"justification_and_finalization" => run::<JustificationAndFinalizationTest<C>>(file),
-		// "crosslinks" => run::<CrosslinksTest, _>(file, &config),
+		"crosslinks" => run::<CrosslinksTest<C>>(file),
 		// "registry_updates" => run::<RegistryUpdatesTest, _>(file, &config),
 		// "blocks" => run::<BlocksTest, _>(file, &config),
 		// "slots" => run::<SlotsTest, _>(file, &config),