pezkuwi-subxt/substrate/frame/ranked-collective/src/tests.rs

// This file is part of Substrate.

// Copyright (C) Parity Technologies (UK) Ltd.
// SPDX-License-Identifier: Apache-2.0

// Licensed under the Apache License, Version 2.0 (the "License");
// you may not use this file except in compliance with the License.
// You may obtain a copy of the License at
//
// 	http://www.apache.org/licenses/LICENSE-2.0
//
// Unless required by applicable law or agreed to in writing, software
// distributed under the License is distributed on an "AS IS" BASIS,
// WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
// See the License for the specific language governing permissions and
// limitations under the License.

//! The crate's tests.

use std::collections::BTreeMap;

use frame_support::{
	assert_noop, assert_ok, derive_impl,
	error::BadOrigin,
	parameter_types,
	traits::{ConstU16, EitherOf, MapSuccess, Polling},
};
use sp_core::Get;
use sp_runtime::{
	traits::{ReduceBy, ReplaceWithDefault},
	BuildStorage,
};

use super::*;
use crate as pallet_ranked_collective;

type Block = frame_system::mocking::MockBlock<Test>;
type Class = Rank;

frame_support::construct_runtime!(
	pub enum Test
	{
		System: frame_system,
		Club: pallet_ranked_collective,
	}
);

#[derive_impl(frame_system::config_preludes::TestDefaultConfig as frame_system::DefaultConfig)]
impl frame_system::Config for Test {
	type Block = Block;
}

#[derive(Clone, PartialEq, Eq, Debug)]
pub enum TestPollState {
	Ongoing(TallyOf<Test>, Rank),
	Completed(u64, bool),
}
use TestPollState::*;

parameter_types! {
	pub static Polls: BTreeMap<u8, TestPollState> = vec![
		(1, Completed(1, true)),
		(2, Completed(2, false)),
		(3, Ongoing(Tally::from_parts(0, 0, 0), 1)),
	].into_iter().collect();
}

pub struct TestPolls;
impl Polling<TallyOf<Test>> for TestPolls {
	type Index = u8;
	type Votes = Votes;
	type Moment = u64;
	type Class = Class;
	fn classes() -> Vec<Self::Class> {
		vec![0, 1, 2]
	}
	fn as_ongoing(index: u8) -> Option<(TallyOf<Test>, Self::Class)> {
		Polls::get().remove(&index).and_then(|x| {
			if let TestPollState::Ongoing(t, c) = x {
				Some((t, c))
			} else {
				None
			}
		})
	}
	fn access_poll<R>(
		index: Self::Index,
		f: impl FnOnce(PollStatus<&mut TallyOf<Test>, Self::Moment, Self::Class>) -> R,
	) -> R {
		let mut polls = Polls::get();
		let entry = polls.get_mut(&index);
		let r = match entry {
			Some(Ongoing(ref mut tally_mut_ref, class)) =>
				f(PollStatus::Ongoing(tally_mut_ref, *class)),
			Some(Completed(when, succeeded)) => f(PollStatus::Completed(*when, *succeeded)),
			None => f(PollStatus::None),
		};
		Polls::set(polls);
		r
	}
	fn try_access_poll<R>(
		index: Self::Index,
		f: impl FnOnce(
			PollStatus<&mut TallyOf<Test>, Self::Moment, Self::Class>,
		) -> Result<R, DispatchError>,
	) -> Result<R, DispatchError> {
		let mut polls = Polls::get();
		let entry = polls.get_mut(&index);
		let r = match entry {
			Some(Ongoing(ref mut tally_mut_ref, class)) =>
				f(PollStatus::Ongoing(tally_mut_ref, *class)),
			Some(Completed(when, succeeded)) => f(PollStatus::Completed(*when, *succeeded)),
			None => f(PollStatus::None),
		}?;
		Polls::set(polls);
		Ok(r)
	}

	#[cfg(feature = "runtime-benchmarks")]
	fn create_ongoing(class: Self::Class) -> Result<Self::Index, ()> {
		let mut polls = Polls::get();
		let i = polls.keys().rev().next().map_or(0, |x| x + 1);
		polls.insert(i, Ongoing(Tally::new(class), class));
		Polls::set(polls);
		Ok(i)
	}

	#[cfg(feature = "runtime-benchmarks")]
	fn end_ongoing(index: Self::Index, approved: bool) -> Result<(), ()> {
		let mut polls = Polls::get();
		match polls.get(&index) {
			Some(Ongoing(..)) => {},
			_ => return Err(()),
		}
		let now = frame_system::Pallet::<Test>::block_number();
		polls.insert(index, Completed(now, approved));
		Polls::set(polls);
		Ok(())
	}
}

/// Convert the tally class into the minimum rank required to vote on the poll.
/// MinRank(Class) = Class - Delta
pub struct MinRankOfClass<Delta>(PhantomData<Delta>);
impl<Delta: Get<Rank>> Convert<Class, Rank> for MinRankOfClass<Delta> {
	fn convert(a: Class) -> Rank {
		a.saturating_sub(Delta::get())
	}
}

parameter_types! {
	pub static MinRankOfClassDelta: Rank = 0;
}

impl Config for Test {
	type WeightInfo = ();
	type RuntimeEvent = RuntimeEvent;
	type AddOrigin = MapSuccess<Self::PromoteOrigin, ReplaceWithDefault<()>>;
	type RemoveOrigin = Self::DemoteOrigin;
	type PromoteOrigin = EitherOf<
		// Root can promote arbitrarily.
		frame_system::EnsureRootWithSuccess<Self::AccountId, ConstU16<65535>>,
		// Members can promote up to the rank of 2 below them.
		MapSuccess<EnsureRanked<Test, (), 2>, ReduceBy<ConstU16<2>>>,
	>;
	type DemoteOrigin = EitherOf<
		// Root can demote arbitrarily.
		frame_system::EnsureRootWithSuccess<Self::AccountId, ConstU16<65535>>,
		// Members can demote up to the rank of 3 below them.
		MapSuccess<EnsureRanked<Test, (), 3>, ReduceBy<ConstU16<3>>>,
	>;
	type ExchangeOrigin = EitherOf<
		// Root can exchange arbitrarily.
		frame_system::EnsureRootWithSuccess<Self::AccountId, ConstU16<65535>>,
		// Members can exchange up to the rank of 2 below them.
		MapSuccess<EnsureRanked<Test, (), 2>, ReduceBy<ConstU16<2>>>,
	>;
	type Polls = TestPolls;
	type MinRankOfClass = MinRankOfClass<MinRankOfClassDelta>;
	type MemberSwappedHandler = ();
	type VoteWeight = Geometric;
	#[cfg(feature = "runtime-benchmarks")]
	type BenchmarkSetup = ();
}

pub struct ExtBuilder {}

impl Default for ExtBuilder {
	fn default() -> Self {
		Self {}
	}
}

impl ExtBuilder {
	pub fn build(self) -> sp_io::TestExternalities {
		let t = frame_system::GenesisConfig::<Test>::default().build_storage().unwrap();
		let mut ext = sp_io::TestExternalities::new(t);
		ext.execute_with(|| System::set_block_number(1));
		ext
	}

	pub fn build_and_execute(self, test: impl FnOnce() -> ()) {
		self.build().execute_with(|| {
			test();
			Club::do_try_state().expect("All invariants must hold after a test");
		})
	}
}

fn next_block() {
	System::set_block_number(System::block_number() + 1);
}

fn member_count(r: Rank) -> MemberIndex {
	MemberCount::<Test>::get(r)
}

#[allow(dead_code)]
fn run_to(n: u64) {
	while System::block_number() < n {
		next_block();
	}
}

fn tally(index: u8) -> TallyOf<Test> {
	<TestPolls as Polling<TallyOf<Test>>>::as_ongoing(index).expect("No poll").0
}

#[test]
#[ignore]
#[should_panic(expected = "No poll")]
fn unknown_poll_should_panic() {
	let _ = tally(0);
}

#[test]
#[ignore]
#[should_panic(expected = "No poll")]
fn completed_poll_should_panic() {
	let _ = tally(1);
}

#[test]
fn basic_stuff() {
	ExtBuilder::default().build_and_execute(|| {
		assert_eq!(tally(3), Tally::from_parts(0, 0, 0));
	});
}

#[test]
fn member_lifecycle_works() {
	ExtBuilder::default().build_and_execute(|| {
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 1));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 1));
		assert_ok!(Club::demote_member(RuntimeOrigin::root(), 1));
		assert_ok!(Club::demote_member(RuntimeOrigin::root(), 1));
		assert_eq!(member_count(0), 0);
		assert_eq!(member_count(1), 0);
	});
}

#[test]
fn add_remove_works() {
	ExtBuilder::default().build_and_execute(|| {
		assert_noop!(Club::add_member(RuntimeOrigin::signed(1), 1), DispatchError::BadOrigin);
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 1));
		assert_eq!(member_count(0), 1);

		assert_ok!(Club::demote_member(RuntimeOrigin::root(), 1));
		assert_eq!(member_count(0), 0);

		assert_ok!(Club::add_member(RuntimeOrigin::root(), 1));
		assert_eq!(member_count(0), 1);

		assert_ok!(Club::add_member(RuntimeOrigin::root(), 2));
		assert_eq!(member_count(0), 2);

		assert_ok!(Club::add_member(RuntimeOrigin::root(), 3));
		assert_eq!(member_count(0), 3);

		assert_ok!(Club::demote_member(RuntimeOrigin::root(), 3));
		assert_eq!(member_count(0), 2);

		assert_ok!(Club::demote_member(RuntimeOrigin::root(), 1));
		assert_eq!(member_count(0), 1);

		assert_ok!(Club::demote_member(RuntimeOrigin::root(), 2));
		assert_eq!(member_count(0), 0);
	});
}

#[test]
fn promote_demote_works() {
	ExtBuilder::default().build_and_execute(|| {
		assert_noop!(Club::add_member(RuntimeOrigin::signed(1), 1), DispatchError::BadOrigin);
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 1));
		assert_eq!(member_count(0), 1);
		assert_eq!(member_count(1), 0);

		assert_ok!(Club::add_member(RuntimeOrigin::root(), 2));
		assert_eq!(member_count(0), 2);
		assert_eq!(member_count(1), 0);

		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 1));
		assert_eq!(member_count(0), 2);
		assert_eq!(member_count(1), 1);

		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 2));
		assert_eq!(member_count(0), 2);
		assert_eq!(member_count(1), 2);

		assert_ok!(Club::demote_member(RuntimeOrigin::root(), 1));
		assert_eq!(member_count(0), 2);
		assert_eq!(member_count(1), 1);

		assert_noop!(Club::demote_member(RuntimeOrigin::signed(1), 1), DispatchError::BadOrigin);
		assert_ok!(Club::demote_member(RuntimeOrigin::root(), 1));
		assert_eq!(member_count(0), 1);
		assert_eq!(member_count(1), 1);
	});
}

#[test]
fn promote_demote_by_rank_works() {
	ExtBuilder::default().build_and_execute(|| {
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 1));
		for _ in 0..7 {
			assert_ok!(Club::promote_member(RuntimeOrigin::root(), 1));
		}

		// #1 can add #2 and promote to rank 1
		assert_ok!(Club::add_member(RuntimeOrigin::signed(1), 2));
		assert_ok!(Club::promote_member(RuntimeOrigin::signed(1), 2));
		// #2 as rank 1 cannot do anything privileged
		assert_noop!(Club::add_member(RuntimeOrigin::signed(2), 3), BadOrigin);

		assert_ok!(Club::promote_member(RuntimeOrigin::signed(1), 2));
		// #2 as rank 2 can add #3.
		assert_ok!(Club::add_member(RuntimeOrigin::signed(2), 3));

		// #2 as rank 2 cannot promote #3 to rank 1
		assert_noop!(
			Club::promote_member(RuntimeOrigin::signed(2), 3),
			Error::<Test>::NoPermission
		);

		// #1 as rank 7 can promote #2 only up to rank 5 and once there cannot demote them.
		assert_ok!(Club::promote_member(RuntimeOrigin::signed(1), 2));
		assert_ok!(Club::promote_member(RuntimeOrigin::signed(1), 2));
		assert_ok!(Club::promote_member(RuntimeOrigin::signed(1), 2));
		assert_noop!(
			Club::promote_member(RuntimeOrigin::signed(1), 2),
			Error::<Test>::NoPermission
		);
		assert_noop!(Club::demote_member(RuntimeOrigin::signed(1), 2), Error::<Test>::NoPermission);

		// #2 as rank 5 can promote #3 only up to rank 3 and once there cannot demote them.
		assert_ok!(Club::promote_member(RuntimeOrigin::signed(2), 3));
		assert_ok!(Club::promote_member(RuntimeOrigin::signed(2), 3));
		assert_ok!(Club::promote_member(RuntimeOrigin::signed(2), 3));
		assert_noop!(
			Club::promote_member(RuntimeOrigin::signed(2), 3),
			Error::<Test>::NoPermission
		);
		assert_noop!(Club::demote_member(RuntimeOrigin::signed(2), 3), Error::<Test>::NoPermission);

		// #2 can add #4 & #5 as rank 0 and #6 & #7 as rank 1.
		assert_ok!(Club::add_member(RuntimeOrigin::signed(2), 4));
		assert_ok!(Club::add_member(RuntimeOrigin::signed(2), 5));
		assert_ok!(Club::add_member(RuntimeOrigin::signed(2), 6));
		assert_ok!(Club::promote_member(RuntimeOrigin::signed(2), 6));
		assert_ok!(Club::add_member(RuntimeOrigin::signed(2), 7));
		assert_ok!(Club::promote_member(RuntimeOrigin::signed(2), 7));

		// #3 as rank 3 can demote/remove #4 & #5 but not #6 & #7
		assert_ok!(Club::demote_member(RuntimeOrigin::signed(3), 4));
		assert_ok!(Club::remove_member(RuntimeOrigin::signed(3), 5, 0));
		assert_noop!(Club::demote_member(RuntimeOrigin::signed(3), 6), Error::<Test>::NoPermission);
		assert_noop!(
			Club::remove_member(RuntimeOrigin::signed(3), 7, 1),
			Error::<Test>::NoPermission
		);

		// #2 as rank 5 can demote/remove #6 & #7
		assert_ok!(Club::demote_member(RuntimeOrigin::signed(2), 6));
		assert_ok!(Club::remove_member(RuntimeOrigin::signed(2), 7, 1));
	});
}

#[test]
fn voting_works() {
	ExtBuilder::default().build_and_execute(|| {
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 0));
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 1));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 1));
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 2));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 2));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 2));
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 3));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 3));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 3));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 3));

		assert_noop!(Club::vote(RuntimeOrigin::signed(0), 3, true), Error::<Test>::RankTooLow);
		assert_eq!(tally(3), Tally::from_parts(0, 0, 0));

		assert_ok!(Club::vote(RuntimeOrigin::signed(1), 3, true));
		assert_eq!(tally(3), Tally::from_parts(1, 1, 0));
		assert_ok!(Club::vote(RuntimeOrigin::signed(1), 3, false));
		assert_eq!(tally(3), Tally::from_parts(0, 0, 1));

		assert_ok!(Club::vote(RuntimeOrigin::signed(2), 3, true));
		assert_eq!(tally(3), Tally::from_parts(1, 3, 1));
		assert_ok!(Club::vote(RuntimeOrigin::signed(2), 3, false));
		assert_eq!(tally(3), Tally::from_parts(0, 0, 4));

		assert_ok!(Club::vote(RuntimeOrigin::signed(3), 3, true));
		assert_eq!(tally(3), Tally::from_parts(1, 6, 4));
		assert_ok!(Club::vote(RuntimeOrigin::signed(3), 3, false));
		assert_eq!(tally(3), Tally::from_parts(0, 0, 10));
	});
}

#[test]
fn cleanup_works() {
	ExtBuilder::default().build_and_execute(|| {
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 1));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 1));
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 2));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 2));
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 3));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 3));

		assert_ok!(Club::vote(RuntimeOrigin::signed(1), 3, true));
		assert_ok!(Club::vote(RuntimeOrigin::signed(2), 3, false));
		assert_ok!(Club::vote(RuntimeOrigin::signed(3), 3, true));

		assert_noop!(Club::cleanup_poll(RuntimeOrigin::signed(4), 3, 10), Error::<Test>::Ongoing);
		Polls::set(
			vec![(1, Completed(1, true)), (2, Completed(2, false)), (3, Completed(3, true))]
				.into_iter()
				.collect(),
		);
		assert_ok!(Club::cleanup_poll(RuntimeOrigin::signed(4), 3, 10));
		// NOTE: This will fail until #10016 is merged.
		//		assert_noop!(Club::cleanup_poll(RuntimeOrigin::signed(4), 3, 10),
		// Error::<Test>::NoneRemaining);
	});
}

#[test]
fn remove_member_cleanup_works() {
	ExtBuilder::default().build_and_execute(|| {
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 1));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 1));
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 2));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 2));
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 3));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 3));

		assert_eq!(IdToIndex::<Test>::get(1, 2), Some(1));
		assert_eq!(IndexToId::<Test>::get(1, 1), Some(2));

		assert_eq!(IdToIndex::<Test>::get(1, 3), Some(2));
		assert_eq!(IndexToId::<Test>::get(1, 2), Some(3));

		assert_ok!(Club::remove_member(RuntimeOrigin::root(), 2, 1));

		assert_eq!(IdToIndex::<Test>::get(1, 2), None);
		assert_eq!(IndexToId::<Test>::get(1, 1), Some(3));

		assert_eq!(IdToIndex::<Test>::get(1, 3), Some(1));
		assert_eq!(IndexToId::<Test>::get(1, 2), None);
	});
}

#[test]
fn ensure_ranked_works() {
	ExtBuilder::default().build_and_execute(|| {
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 1));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 1));
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 2));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 2));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 2));
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 3));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 3));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 3));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 3));

		use frame_support::traits::OriginTrait;
		type Rank1 = EnsureRanked<Test, (), 1>;
		type Rank2 = EnsureRanked<Test, (), 2>;
		type Rank3 = EnsureRanked<Test, (), 3>;
		type Rank4 = EnsureRanked<Test, (), 4>;
		assert_eq!(<Rank1 as EnsureOrigin<_>>::try_origin(RuntimeOrigin::signed(1)).unwrap(), 1);
		assert_eq!(<Rank1 as EnsureOrigin<_>>::try_origin(RuntimeOrigin::signed(2)).unwrap(), 2);
		assert_eq!(<Rank1 as EnsureOrigin<_>>::try_origin(RuntimeOrigin::signed(3)).unwrap(), 3);
		assert_eq!(
			<Rank2 as EnsureOrigin<_>>::try_origin(RuntimeOrigin::signed(1))
				.unwrap_err()
				.into_signer()
				.unwrap(),
			1
		);
		assert_eq!(<Rank2 as EnsureOrigin<_>>::try_origin(RuntimeOrigin::signed(2)).unwrap(), 2);
		assert_eq!(<Rank2 as EnsureOrigin<_>>::try_origin(RuntimeOrigin::signed(3)).unwrap(), 3);
		assert_eq!(
			<Rank3 as EnsureOrigin<_>>::try_origin(RuntimeOrigin::signed(1))
				.unwrap_err()
				.into_signer()
				.unwrap(),
			1
		);
		assert_eq!(
			<Rank3 as EnsureOrigin<_>>::try_origin(RuntimeOrigin::signed(2))
				.unwrap_err()
				.into_signer()
				.unwrap(),
			2
		);
		assert_eq!(<Rank3 as EnsureOrigin<_>>::try_origin(RuntimeOrigin::signed(3)).unwrap(), 3);
		assert_eq!(
			<Rank4 as EnsureOrigin<_>>::try_origin(RuntimeOrigin::signed(1))
				.unwrap_err()
				.into_signer()
				.unwrap(),
			1
		);
		assert_eq!(
			<Rank4 as EnsureOrigin<_>>::try_origin(RuntimeOrigin::signed(2))
				.unwrap_err()
				.into_signer()
				.unwrap(),
			2
		);
		assert_eq!(
			<Rank4 as EnsureOrigin<_>>::try_origin(RuntimeOrigin::signed(3))
				.unwrap_err()
				.into_signer()
				.unwrap(),
			3
		);
	});
}

#[test]
fn do_add_member_to_rank_works() {
	ExtBuilder::default().build_and_execute(|| {
		let max_rank = 9u16;
		assert_ok!(Club::do_add_member_to_rank(69, max_rank / 2, true));
		assert_ok!(Club::do_add_member_to_rank(1337, max_rank, true));
		for i in 0..=max_rank {
			if i <= max_rank / 2 {
				assert_eq!(member_count(i), 2);
			} else {
				assert_eq!(member_count(i), 1);
			}
		}
		assert_eq!(member_count(max_rank + 1), 0);
	})
}

#[test]
fn tally_support_correct() {
	ExtBuilder::default().build_and_execute(|| {
		// add members,
		// rank 1: accounts 1, 2, 3
		// rank 2: accounts 2, 3
		// rank 3: accounts 3.
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 1));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 1));
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 2));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 2));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 2));
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 3));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 3));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 3));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 3));

		// init tally with 1 aye vote.
		let tally: TallyOf<Test> = Tally::from_parts(1, 1, 0);

		// with minRank(Class) = Class
		// for class 3, 100% support.
		MinRankOfClassDelta::set(0);
		assert_eq!(tally.support(3), Perbill::from_rational(1u32, 1));

		// with minRank(Class) = (Class - 1)
		// for class 3, ~50% support.
		MinRankOfClassDelta::set(1);
		assert_eq!(tally.support(3), Perbill::from_rational(1u32, 2));

		// with minRank(Class) = (Class - 2)
		// for class 3, ~33% support.
		MinRankOfClassDelta::set(2);
		assert_eq!(tally.support(3), Perbill::from_rational(1u32, 3));

		// reset back.
		MinRankOfClassDelta::set(0);
	});
}

#[test]
fn exchange_member_works() {
	ExtBuilder::default().build_and_execute(|| {
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 1));
		assert_eq!(member_count(0), 1);

		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 1));

		let member_record = MemberRecord { rank: 1 };
		assert_eq!(Members::<Test>::get(1), Some(member_record.clone()));
		assert_eq!(Members::<Test>::get(2), None);

		assert_ok!(Club::exchange_member(RuntimeOrigin::root(), 1, 2));
		assert_eq!(member_count(0), 1);

		assert_eq!(Members::<Test>::get(1), None);
		assert_eq!(Members::<Test>::get(2), Some(member_record));

		assert_ok!(Club::add_member(RuntimeOrigin::root(), 3));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 3));

		assert_noop!(
			Club::exchange_member(RuntimeOrigin::signed(3), 2, 1),
			DispatchError::BadOrigin
		);
	});
}

#[test]
fn exchange_member_same_noops() {
	ExtBuilder::default().build_and_execute(|| {
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 1));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 1));
		assert_ok!(Club::add_member(RuntimeOrigin::root(), 2));
		assert_ok!(Club::promote_member(RuntimeOrigin::root(), 2));

		// Swapping the same accounts is a noop:
		assert_noop!(Club::exchange_member(RuntimeOrigin::root(), 1, 1), Error::<Test>::SameMember);
		// Swapping with a different member is a noop:
		assert_noop!(
			Club::exchange_member(RuntimeOrigin::root(), 1, 2),
			Error::<Test>::AlreadyMember
		);
	});
}