Rename Palette to FRAME (#4182)

* palette -> frame

* PALETTE, Palette -> FRAME

* Move folder pallete -> frame

* Update docs/Structure.adoc

Co-Authored-By: Benjamin Kampmann <ben.kampmann@googlemail.com>

* Update docs/README.adoc

Co-Authored-By: Benjamin Kampmann <ben.kampmann@googlemail.com>

* Update README.adoc

substrate/frame/session/src/historical.rs

@@ -0,0 +1,431 @@
+// Copyright 2019 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! An opt-in utility for tracking historical sessions in SRML-session.
+//!
+//! This is generally useful when implementing blockchains that require accountable
+//! safety where validators from some amount f prior sessions must remain slashable.
+//!
+//! Rather than store the full session data for any given session, we instead commit
+//! to the roots of merkle tries containing the session data.
+//!
+//! These roots and proofs of inclusion can be generated at any time during the current session.
+//! Afterwards, the proofs can be fed to a consensus module when reporting misbehavior.
+
+use rstd::prelude::*;
+use codec::{Encode, Decode};
+use sr_primitives::KeyTypeId;
+use sr_primitives::traits::{Convert, OpaqueKeys, Hash as HashT};
+use support::{decl_module, decl_storage};
+use support::{Parameter, print};
+use substrate_trie::{MemoryDB, Trie, TrieMut, Recorder, EMPTY_PREFIX};
+use substrate_trie::trie_types::{TrieDBMut, TrieDB};
+use super::{SessionIndex, Module as SessionModule};
+
+type ValidatorCount = u32;
+
+/// Trait necessary for the historical module.
+pub trait Trait: super::Trait {
+	/// Full identification of the validator.
+	type FullIdentification: Parameter;
+
+	/// A conversion from validator ID to full identification.
+	///
+	/// This should contain any references to economic actors associated with the
+	/// validator, since they may be outdated by the time this is queried from a
+	/// historical trie.
+	///
+	/// This mapping is expected to remain stable in between calls to
+	/// `Self::OnSessionEnding::on_session_ending` which return new validators.
+	type FullIdentificationOf: Convert<Self::ValidatorId, Option<Self::FullIdentification>>;
+}
+
+decl_storage! {
+	trait Store for Module<T: Trait> as Session {
+		/// Mapping from historical session indices to session-data root hash and validator count.
+		HistoricalSessions get(fn historical_root): map SessionIndex => Option<(T::Hash, ValidatorCount)>;
+		/// Queued full identifications for queued sessions whose validators have become obsolete.
+		CachedObsolete get(fn cached_obsolete): map SessionIndex
+			=> Option<Vec<(T::ValidatorId, T::FullIdentification)>>;
+		/// The range of historical sessions we store. [first, last)
+		StoredRange: Option<(SessionIndex, SessionIndex)>;
+	}
+}
+
+decl_module! {
+	pub struct Module<T: Trait> for enum Call where origin: T::Origin { }
+}
+
+impl<T: Trait> Module<T> {
+	/// Prune historical stored session roots up to (but not including)
+	/// `up_to`.
+	pub fn prune_up_to(up_to: SessionIndex) {
+		<Self as Store>::StoredRange::mutate(|range| {
+			let (start, end) = match *range {
+				Some(range) => range,
+				None => return, // nothing to prune.
+			};
+
+			let up_to = rstd::cmp::min(up_to, end);
+
+			if up_to < start {
+				return // out of bounds. harmless.
+			}
+
+			(start..up_to).for_each(<Self as Store>::HistoricalSessions::remove);
+
+			let new_start = up_to;
+			*range = if new_start == end {
+				None // nothing is stored.
+			} else {
+				Some((new_start, end))
+			}
+		})
+	}
+}
+
+/// Specialization of the crate-level `OnSessionEnding` which returns the old
+/// set of full identification when changing the validator set.
+pub trait OnSessionEnding<ValidatorId, FullIdentification>: crate::OnSessionEnding<ValidatorId> {
+	/// If there was a validator set change, its returns the set of new validators along with the
+	/// old validators and their full identifications.
+	fn on_session_ending(ending: SessionIndex, will_apply_at: SessionIndex)
+		-> Option<(Vec<ValidatorId>, Vec<(ValidatorId, FullIdentification)>)>;
+}
+
+/// An `OnSessionEnding` implementation that wraps an inner `I` and also
+/// sets the historical trie root of the ending session.
+pub struct NoteHistoricalRoot<T, I>(rstd::marker::PhantomData<(T, I)>);
+
+impl<T: Trait, I> crate::OnSessionEnding<T::ValidatorId> for NoteHistoricalRoot<T, I>
+	where I: OnSessionEnding<T::ValidatorId, T::FullIdentification>
+{
+	fn on_session_ending(ending: SessionIndex, applied_at: SessionIndex) -> Option<Vec<T::ValidatorId>> {
+		StoredRange::mutate(|range| {
+			range.get_or_insert_with(|| (ending, ending)).1 = ending + 1;
+		});
+
+		// do all of this _before_ calling the other `on_session_ending` impl
+		// so that we have e.g. correct exposures from the _current_.
+
+		let count = <SessionModule<T>>::validators().len() as u32;
+		match ProvingTrie::<T>::generate_for(ending) {
+			Ok(trie) => <HistoricalSessions<T>>::insert(ending, &(trie.root, count)),
+			Err(reason) => {
+				print("Failed to generate historical ancestry-inclusion proof.");
+				print(reason);
+			}
+		};
+
+		// trie has been generated for this session, so it's no longer queued.
+		<CachedObsolete<T>>::remove(&ending);
+
+		let (new_validators, old_exposures) = <I as OnSessionEnding<_, _>>::on_session_ending(ending, applied_at)?;
+
+		// every session from `ending+1 .. applied_at` now has obsolete `FullIdentification`
+		// now that a new validator election has occurred.
+		// we cache these in the trie until those sessions themselves end.
+		for obsolete in (ending + 1) .. applied_at {
+			<CachedObsolete<T>>::insert(obsolete, &old_exposures);
+		}
+
+		Some(new_validators)
+	}
+}
+
+type HasherOf<T> = <<T as system::Trait>::Hashing as HashT>::Hasher;
+
+/// A tuple of the validator's ID and their full identification.
+pub type IdentificationTuple<T> = (<T as crate::Trait>::ValidatorId, <T as Trait>::FullIdentification);
+
+/// a trie instance for checking and generating proofs.
+pub struct ProvingTrie<T: Trait> {
+	db: MemoryDB<HasherOf<T>>,
+	root: T::Hash,
+}
+
+impl<T: Trait> ProvingTrie<T> {
+	fn generate_for(now: SessionIndex) -> Result<Self, &'static str> {
+		let mut db = MemoryDB::default();
+		let mut root = Default::default();
+
+		fn build<T: Trait, I>(root: &mut T::Hash, db: &mut MemoryDB<HasherOf<T>>, validators: I)
+			-> Result<(), &'static str>
+			where I: IntoIterator<Item=(T::ValidatorId, Option<T::FullIdentification>)>
+		{
+			let mut trie = TrieDBMut::new(db, root);
+			for (i, (validator, full_id)) in validators.into_iter().enumerate() {
+				let i = i as u32;
+				let keys = match <SessionModule<T>>::load_keys(&validator) {
+					None => continue,
+					Some(k) => k,
+				};
+
+				let full_id = full_id.or_else(|| T::FullIdentificationOf::convert(validator.clone()));
+				let full_id = match full_id {
+					None => return Err("no full identification for a current validator"),
+					Some(full) => (validator, full),
+				};
+
+				// map each key to the owner index.
+				for key_id in T::Keys::key_ids() {
+					let key = keys.get_raw(*key_id);
+					let res = (key_id, key).using_encoded(|k|
+						i.using_encoded(|v| trie.insert(k, v))
+					);
+
+					let _ = res.map_err(|_| "failed to insert into trie")?;
+				}
+
+				// map each owner index to the full identification.
+				let _ = i.using_encoded(|k| full_id.using_encoded(|v| trie.insert(k, v)))
+					.map_err(|_| "failed to insert into trie")?;
+			}
+
+			Ok(())
+		}
+
+		// if the current session's full identifications are obsolete but cached,
+		// use those.
+		if let Some(obsolete) = <CachedObsolete<T>>::get(&now) {
+			build::<T, _>(&mut root, &mut db, obsolete.into_iter().map(|(v, f)| (v, Some(f))))?
+		} else {
+			let validators = <SessionModule<T>>::validators();
+			build::<T, _>(&mut root, &mut db, validators.into_iter().map(|v| (v, None)))?
+		}
+
+		Ok(ProvingTrie {
+			db,
+			root,
+		})
+	}
+
+	fn from_nodes(root: T::Hash, nodes: &[Vec<u8>]) -> Self {
+		use substrate_trie::HashDBT;
+
+		let mut memory_db = MemoryDB::default();
+		for node in nodes {
+			HashDBT::insert(&mut memory_db, EMPTY_PREFIX, &node[..]);
+		}
+
+		ProvingTrie {
+			db: memory_db,
+			root,
+		}
+	}
+
+	/// Prove the full verification data for a given key and key ID.
+	pub fn prove(&self, key_id: KeyTypeId, key_data: &[u8]) -> Option<Vec<Vec<u8>>> {
+		let trie = TrieDB::new(&self.db, &self.root).ok()?;
+		let mut recorder = Recorder::new();
+		let val_idx = (key_id, key_data).using_encoded(|s| {
+			trie.get_with(s, &mut recorder)
+				.ok()?
+				.and_then(|raw| u32::decode(&mut &*raw).ok())
+		})?;
+
+		val_idx.using_encoded(|s| {
+			trie.get_with(s, &mut recorder)
+				.ok()?
+				.and_then(|raw| <IdentificationTuple<T>>::decode(&mut &*raw).ok())
+		})?;
+
+		Some(recorder.drain().into_iter().map(|r| r.data).collect())
+	}
+
+	/// Access the underlying trie root.
+	pub fn root(&self) -> &T::Hash {
+		&self.root
+	}
+
+	// Check a proof contained within the current memory-db. Returns `None` if the
+	// nodes within the current `MemoryDB` are insufficient to query the item.
+	fn query(&self, key_id: KeyTypeId, key_data: &[u8]) -> Option<IdentificationTuple<T>> {
+		let trie = TrieDB::new(&self.db, &self.root).ok()?;
+		let val_idx = (key_id, key_data).using_encoded(|s| trie.get(s))
+			.ok()?
+			.and_then(|raw| u32::decode(&mut &*raw).ok())?;
+
+		val_idx.using_encoded(|s| trie.get(s))
+			.ok()?
+			.and_then(|raw| <IdentificationTuple<T>>::decode(&mut &*raw).ok())
+	}
+
+}
+
+/// Proof of ownership of a specific key.
+#[derive(Encode, Decode, Clone)]
+pub struct Proof {
+	session: SessionIndex,
+	trie_nodes: Vec<Vec<u8>>,
+}
+
+impl<T: Trait, D: AsRef<[u8]>> support::traits::KeyOwnerProofSystem<(KeyTypeId, D)>
+	for Module<T>
+{
+	type Proof = Proof;
+	type IdentificationTuple = IdentificationTuple<T>;
+
+	fn prove(key: (KeyTypeId, D)) -> Option<Self::Proof> {
+		let session = <SessionModule<T>>::current_index();
+		let trie = ProvingTrie::<T>::generate_for(session).ok()?;
+
+		let (id, data) = key;
+
+		trie.prove(id, data.as_ref()).map(|trie_nodes| Proof {
+			session,
+			trie_nodes,
+		})
+	}
+
+	fn check_proof(key: (KeyTypeId, D), proof: Proof) -> Option<IdentificationTuple<T>> {
+		let (id, data) = key;
+
+		if proof.session == <SessionModule<T>>::current_index() {
+			<SessionModule<T>>::key_owner(id, data.as_ref()).and_then(|owner|
+				T::FullIdentificationOf::convert(owner.clone()).map(move |id| (owner, id))
+			)
+		} else {
+			let (root, _) = <HistoricalSessions<T>>::get(&proof.session)?;
+			let trie = ProvingTrie::<T>::from_nodes(root, &proof.trie_nodes);
+
+			trie.query(id, data.as_ref())
+		}
+	}
+}
+
+#[cfg(test)]
+mod tests {
+	use super::*;
+	use primitives::crypto::key_types::DUMMY;
+	use sr_primitives::{traits::OnInitialize, testing::UintAuthorityId};
+	use crate::mock::{
+		NEXT_VALIDATORS, force_new_session,
+		set_next_validators, Test, System, Session,
+	};
+	use support::traits::KeyOwnerProofSystem;
+
+	type Historical = Module<Test>;
+
+	fn new_test_ext() -> runtime_io::TestExternalities {
+		let mut t = system::GenesisConfig::default().build_storage::<Test>().unwrap();
+		crate::GenesisConfig::<Test> {
+			keys: NEXT_VALIDATORS.with(|l|
+				l.borrow().iter().cloned().map(|i| (i, UintAuthorityId(i).into())).collect()
+			),
+		}.assimilate_storage(&mut t).unwrap();
+		runtime_io::TestExternalities::new(t)
+	}
+
+	#[test]
+	fn generated_proof_is_good() {
+		new_test_ext().execute_with(|| {
+			set_next_validators(vec![1, 2]);
+			force_new_session();
+
+			System::set_block_number(1);
+			Session::on_initialize(1);
+
+			let encoded_key_1 = UintAuthorityId(1).encode();
+			let proof = Historical::prove((DUMMY, &encoded_key_1[..])).unwrap();
+
+			// proof-checking in the same session is OK.
+			assert!(Historical::check_proof((DUMMY, &encoded_key_1[..]), proof.clone()).is_some());
+
+			set_next_validators(vec![1, 2, 4]);
+			force_new_session();
+
+			assert!(Historical::cached_obsolete(&(proof.session + 1)).is_none());
+
+			System::set_block_number(2);
+			Session::on_initialize(2);
+
+			assert!(Historical::cached_obsolete(&(proof.session + 1)).is_some());
+
+			assert!(Historical::historical_root(proof.session).is_some());
+			assert!(Session::current_index() > proof.session);
+
+			// proof-checking in the next session is also OK.
+			assert!(Historical::check_proof((DUMMY, &encoded_key_1[..]), proof.clone()).is_some());
+
+			set_next_validators(vec![1, 2, 5]);
+
+			force_new_session();
+			System::set_block_number(3);
+			Session::on_initialize(3);
+
+			assert!(Historical::cached_obsolete(&(proof.session + 1)).is_none());
+		});
+	}
+
+	#[test]
+	fn prune_up_to_works() {
+		new_test_ext().execute_with(|| {
+			for i in 1..101u64 {
+				set_next_validators(vec![i]);
+				force_new_session();
+
+				System::set_block_number(i);
+				Session::on_initialize(i);
+
+			}
+
+			assert_eq!(StoredRange::get(), Some((0, 100)));
+
+			for i in 1..100 {
+				assert!(Historical::historical_root(i).is_some())
+			}
+
+			Historical::prune_up_to(10);
+			assert_eq!(StoredRange::get(), Some((10, 100)));
+
+			Historical::prune_up_to(9);
+			assert_eq!(StoredRange::get(), Some((10, 100)));
+
+			for i in 10..100 {
+				assert!(Historical::historical_root(i).is_some())
+			}
+
+			Historical::prune_up_to(99);
+			assert_eq!(StoredRange::get(), Some((99, 100)));
+
+			Historical::prune_up_to(100);
+			assert_eq!(StoredRange::get(), None);
+
+			for i in 101..201u64 {
+				set_next_validators(vec![i]);
+				force_new_session();
+
+				System::set_block_number(i);
+				Session::on_initialize(i);
+
+			}
+
+			assert_eq!(StoredRange::get(), Some((100, 200)));
+
+			for i in 101..200 {
+				assert!(Historical::historical_root(i).is_some())
+			}
+
+			Historical::prune_up_to(9999);
+			assert_eq!(StoredRange::get(), None);
+
+			for i in 101..200 {
+				assert!(Historical::historical_root(i).is_none())
+			}
+		});
+	}
+}

substrate/frame/session/src/mock.rs

@@ -0,0 +1,211 @@
+// Copyright 2019 Parity Technologies (UK) Ltd.
+// This file is part of Substrate.
+
+// Substrate is free software: you can redistribute it and/or modify
+// it under the terms of the GNU General Public License as published by
+// the Free Software Foundation, either version 3 of the License, or
+// (at your option) any later version.
+
+// Substrate is distributed in the hope that it will be useful,
+// but WITHOUT ANY WARRANTY; without even the implied warranty of
+// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+// GNU General Public License for more details.
+
+// You should have received a copy of the GNU General Public License
+// along with Substrate.  If not, see <http://www.gnu.org/licenses/>.
+
+//! Mock helpers for Session.
+
+use super::*;
+use std::cell::RefCell;
+use support::{impl_outer_origin, parameter_types};
+use primitives::{crypto::key_types::DUMMY, H256};
+use sr_primitives::{
+	Perbill, impl_opaque_keys, traits::{BlakeTwo256, IdentityLookup, ConvertInto},
+	testing::{Header, UintAuthorityId}
+};
+use sr_staking_primitives::SessionIndex;
+
+impl_opaque_keys! {
+	pub struct MockSessionKeys {
+		pub dummy: UintAuthorityId,
+	}
+}
+
+impl From<UintAuthorityId> for MockSessionKeys {
+	fn from(dummy: UintAuthorityId) -> Self {
+		Self { dummy }
+	}
+}
+
+impl_outer_origin! {
+	pub enum Origin for Test {}
+}
+
+thread_local! {
+	pub static VALIDATORS: RefCell<Vec<u64>> = RefCell::new(vec![1, 2, 3]);
+	pub static NEXT_VALIDATORS: RefCell<Vec<u64>> = RefCell::new(vec![1, 2, 3]);
+	pub static AUTHORITIES: RefCell<Vec<UintAuthorityId>> =
+		RefCell::new(vec![UintAuthorityId(1), UintAuthorityId(2), UintAuthorityId(3)]);
+	pub static FORCE_SESSION_END: RefCell<bool> = RefCell::new(false);
+	pub static SESSION_LENGTH: RefCell<u64> = RefCell::new(2);
+	pub static SESSION_CHANGED: RefCell<bool> = RefCell::new(false);
+	pub static TEST_SESSION_CHANGED: RefCell<bool> = RefCell::new(false);
+	pub static DISABLED: RefCell<bool> = RefCell::new(false);
+	// Stores if `on_before_session_end` was called
+	pub static BEFORE_SESSION_END_CALLED: RefCell<bool> = RefCell::new(false);
+}
+
+pub struct TestShouldEndSession;
+impl ShouldEndSession<u64> for TestShouldEndSession {
+	fn should_end_session(now: u64) -> bool {
+		let l = SESSION_LENGTH.with(|l| *l.borrow());
+		now % l == 0 || FORCE_SESSION_END.with(|l| { let r = *l.borrow(); *l.borrow_mut() = false; r })
+	}
+}
+
+pub struct TestSessionHandler;
+impl SessionHandler<u64> for TestSessionHandler {
+	const KEY_TYPE_IDS: &'static [sr_primitives::KeyTypeId] = &[UintAuthorityId::ID];
+	fn on_genesis_session<T: OpaqueKeys>(_validators: &[(u64, T)]) {}
+	fn on_new_session<T: OpaqueKeys>(
+		changed: bool,
+		validators: &[(u64, T)],
+		_queued_validators: &[(u64, T)],
+	) {
+		SESSION_CHANGED.with(|l| *l.borrow_mut() = changed);
+		AUTHORITIES.with(|l|
+			*l.borrow_mut() = validators.iter()
+				.map(|(_, id)| id.get::<UintAuthorityId>(DUMMY).unwrap_or_default())
+				.collect()
+		);
+	}
+	fn on_disabled(_validator_index: usize) {
+		DISABLED.with(|l| *l.borrow_mut() = true)
+	}
+	fn on_before_session_ending() {
+		BEFORE_SESSION_END_CALLED.with(|b| *b.borrow_mut() = true);
+	}
+}
+
+pub struct TestOnSessionEnding;
+impl OnSessionEnding<u64> for TestOnSessionEnding {
+	fn on_session_ending(_: SessionIndex, _: SessionIndex) -> Option<Vec<u64>> {
+		if !TEST_SESSION_CHANGED.with(|l| *l.borrow()) {
+			VALIDATORS.with(|v| {
+				let mut v = v.borrow_mut();
+				*v = NEXT_VALIDATORS.with(|l| l.borrow().clone());
+				Some(v.clone())
+			})
+		} else if DISABLED.with(|l| std::mem::replace(&mut *l.borrow_mut(), false)) {
+			// If there was a disabled validator, underlying conditions have changed
+			// so we return `Some`.
+			Some(VALIDATORS.with(|v| v.borrow().clone()))
+		} else {
+			None
+		}
+	}
+}
+
+#[cfg(feature = "historical")]
+impl crate::historical::OnSessionEnding<u64, u64> for TestOnSessionEnding {
+	fn on_session_ending(ending_index: SessionIndex, will_apply_at: SessionIndex)
+		-> Option<(Vec<u64>, Vec<(u64, u64)>)>
+	{
+		let pair_with_ids = |vals: &[u64]| vals.iter().map(|&v| (v, v)).collect::<Vec<_>>();
+		<Self as OnSessionEnding<_>>::on_session_ending(ending_index, will_apply_at)
+			.map(|vals| (pair_with_ids(&vals), vals))
+			.map(|(ids, vals)| (vals, ids))
+	}
+}
+
+pub fn authorities() -> Vec<UintAuthorityId> {
+	AUTHORITIES.with(|l| l.borrow().to_vec())
+}
+
+pub fn force_new_session() {
+	FORCE_SESSION_END.with(|l| *l.borrow_mut() = true )
+}
+
+pub fn set_session_length(x: u64) {
+	SESSION_LENGTH.with(|l| *l.borrow_mut() = x )
+}
+
+pub fn session_changed() -> bool {
+	SESSION_CHANGED.with(|l| *l.borrow())
+}
+
+pub fn set_next_validators(next: Vec<u64>) {
+	NEXT_VALIDATORS.with(|v| *v.borrow_mut() = next);
+}
+
+pub fn before_session_end_called() -> bool {
+	BEFORE_SESSION_END_CALLED.with(|b| *b.borrow())
+}
+
+pub fn reset_before_session_end_called() {
+	BEFORE_SESSION_END_CALLED.with(|b| *b.borrow_mut() = false);
+}
+
+#[derive(Clone, Eq, PartialEq)]
+pub struct Test;
+
+parameter_types! {
+	pub const BlockHashCount: u64 = 250;
+	pub const MaximumBlockWeight: u32 = 1024;
+	pub const MaximumBlockLength: u32 = 2 * 1024;
+	pub const MinimumPeriod: u64 = 5;
+	pub const AvailableBlockRatio: Perbill = Perbill::one();
+}
+
+impl system::Trait for Test {
+	type Origin = Origin;
+	type Index = u64;
+	type BlockNumber = u64;
+	type Call = ();
+	type Hash = H256;
+	type Hashing = BlakeTwo256;
+	type AccountId = u64;
+	type Lookup = IdentityLookup<Self::AccountId>;
+	type Header = Header;
+	type Event = ();
+	type BlockHashCount = BlockHashCount;
+	type MaximumBlockWeight = MaximumBlockWeight;
+	type AvailableBlockRatio = AvailableBlockRatio;
+	type MaximumBlockLength = MaximumBlockLength;
+	type Version = ();
+}
+
+impl timestamp::Trait for Test {
+	type Moment = u64;
+	type OnTimestampSet = ();
+	type MinimumPeriod = MinimumPeriod;
+}
+
+parameter_types! {
+	pub const DisabledValidatorsThreshold: Perbill = Perbill::from_percent(33);
+}
+
+impl Trait for Test {
+	type ShouldEndSession = TestShouldEndSession;
+	#[cfg(feature = "historical")]
+	type OnSessionEnding = crate::historical::NoteHistoricalRoot<Test, TestOnSessionEnding>;
+	#[cfg(not(feature = "historical"))]
+	type OnSessionEnding = TestOnSessionEnding;
+	type SessionHandler = TestSessionHandler;
+	type ValidatorId = u64;
+	type ValidatorIdOf = ConvertInto;
+	type Keys = MockSessionKeys;
+	type Event = ();
+	type SelectInitialValidators = ();
+	type DisabledValidatorsThreshold = DisabledValidatorsThreshold;
+}
+
+#[cfg(feature = "historical")]
+impl crate::historical::Trait for Test {
+	type FullIdentification = u64;
+	type FullIdentificationOf = sr_primitives::traits::ConvertInto;
+}
+
+pub type System = system::Module<Test>;
+pub type Session = Module<Test>;