Moving pallet-asset-tx-payment from cumulus to substrate (#10127)

* Moving `pallet-asset-tx-payment` from cumulus * move pallet-asset-tx-payment into transaction payment directory * cargo +nightly fmt * Adding `pallet-asset-tx-payment` to node runtime I had to change the Balance type to u128. Also harmonised that pallet's version * Updating cargo.lock after merge * forgot this * Adding tx-payment signature * Missed one more * `transaction-payment` replaced in`SignedExtension` by `asset-tx-payment` and not added * Fixing benches * add test to verify that we don't charge on post-dispatch if we didn't on pre-dispatch * add (failing) test for asset tx payment of unsigned extrinsics * fix test by removing debug_assert * cargo +nightly fmt * typo in `Cargo.lock` * Object defined twice in lock file * cargo update * remove todo * Apply formatting suggestions from code review Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com> * Refactoring `post_dispatch` of `asset-tx-payment` to reuse `post_dispatch` of `transaction-payment` if the fee asset is native Removing unneeded imports. * Removing redundant `TODO` * Reverting an accidental bump of `impl-serde` from `0.3.1` to `0.3.2` * Revert unneeded changes to `cargo.lock` * Update frame/transaction-payment/asset-tx-payment/src/payment.rs Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com> * Fixing cargo fmt Reverting changes which broke cargo fmt Co-authored-by: Alexander Popiak <alexander.popiak@parity.io> Co-authored-by: Alexander Popiak <alexander.popiak@gmail.com> Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>
2026-05-30 15:11:02 +00:00 · 2021-11-19 09:29:12 +00:00
parent 69478639b3
commit 439af98e55
16 changed files with 1346 additions and 11 deletions
@@ -0,0 +1,748 @@
+// Copyright (C) 2021 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.
+
+use super::*;
+use crate as pallet_asset_tx_payment;
+
+use frame_support::{
+	assert_ok,
+	pallet_prelude::*,
+	parameter_types,
+	traits::{fungibles::Mutate, FindAuthor},
+	weights::{
+		DispatchClass, DispatchInfo, PostDispatchInfo, Weight, WeightToFeeCoefficient,
+		WeightToFeeCoefficients, WeightToFeePolynomial,
+	},
+	ConsensusEngineId,
+};
+use frame_system as system;
+use frame_system::EnsureRoot;
+use pallet_balances::Call as BalancesCall;
+use pallet_transaction_payment::CurrencyAdapter;
+use smallvec::smallvec;
+use sp_core::H256;
+use sp_runtime::{
+	testing::Header,
+	traits::{BlakeTwo256, ConvertInto, IdentityLookup, StaticLookup},
+	Perbill,
+};
+use std::cell::RefCell;
+
+type UncheckedExtrinsic = frame_system::mocking::MockUncheckedExtrinsic<Runtime>;
+type Block = frame_system::mocking::MockBlock<Runtime>;
+type Balance = u64;
+type AccountId = u64;
+
+frame_support::construct_runtime!(
+	pub enum Runtime where
+		Block = Block,
+		NodeBlock = Block,
+		UncheckedExtrinsic = UncheckedExtrinsic,
+	{
+		System: system::{Pallet, Call, Config, Storage, Event<T>},
+		Balances: pallet_balances::{Pallet, Call, Storage, Config<T>, Event<T>},
+		TransactionPayment: pallet_transaction_payment::{Pallet, Storage},
+		Assets: pallet_assets::{Pallet, Call, Storage, Event<T>},
+		Authorship: pallet_authorship::{Pallet, Call, Storage},
+		AssetTxPayment: pallet_asset_tx_payment::{Pallet},
+	}
+);
+
+const CALL: &<Runtime as frame_system::Config>::Call =
+	&Call::Balances(BalancesCall::transfer { dest: 2, value: 69 });
+
+thread_local! {
+	static EXTRINSIC_BASE_WEIGHT: RefCell<u64> = RefCell::new(0);
+}
+
+pub struct BlockWeights;
+impl Get<frame_system::limits::BlockWeights> for BlockWeights {
+	fn get() -> frame_system::limits::BlockWeights {
+		frame_system::limits::BlockWeights::builder()
+			.base_block(0)
+			.for_class(DispatchClass::all(), |weights| {
+				weights.base_extrinsic = EXTRINSIC_BASE_WEIGHT.with(|v| *v.borrow()).into();
+			})
+			.for_class(DispatchClass::non_mandatory(), |weights| {
+				weights.max_total = 1024.into();
+			})
+			.build_or_panic()
+	}
+}
+
+parameter_types! {
+	pub const BlockHashCount: u64 = 250;
+	pub static TransactionByteFee: u64 = 1;
+	pub static WeightToFee: u64 = 1;
+}
+
+impl frame_system::Config for Runtime {
+	type BaseCallFilter = frame_support::traits::Everything;
+	type BlockWeights = BlockWeights;
+	type BlockLength = ();
+	type DbWeight = ();
+	type Origin = Origin;
+	type Index = u64;
+	type BlockNumber = u64;
+	type Call = Call;
+	type Hash = H256;
+	type Hashing = BlakeTwo256;
+	type AccountId = AccountId;
+	type Lookup = IdentityLookup<Self::AccountId>;
+	type Header = Header;
+	type Event = Event;
+	type BlockHashCount = BlockHashCount;
+	type Version = ();
+	type PalletInfo = PalletInfo;
+	type AccountData = pallet_balances::AccountData<u64>;
+	type OnNewAccount = ();
+	type OnKilledAccount = ();
+	type SystemWeightInfo = ();
+	type SS58Prefix = ();
+	type OnSetCode = ();
+}
+
+parameter_types! {
+	pub const ExistentialDeposit: u64 = 10;
+	pub const MaxReserves: u32 = 50;
+}
+
+impl pallet_balances::Config for Runtime {
+	type Balance = Balance;
+	type Event = Event;
+	type DustRemoval = ();
+	type ExistentialDeposit = ExistentialDeposit;
+	type AccountStore = System;
+	type MaxLocks = ();
+	type WeightInfo = ();
+	type MaxReserves = MaxReserves;
+	type ReserveIdentifier = [u8; 8];
+}
+
+impl WeightToFeePolynomial for WeightToFee {
+	type Balance = u64;
+
+	fn polynomial() -> WeightToFeeCoefficients<Self::Balance> {
+		smallvec![WeightToFeeCoefficient {
+			degree: 1,
+			coeff_frac: Perbill::zero(),
+			coeff_integer: WEIGHT_TO_FEE.with(|v| *v.borrow()),
+			negative: false,
+		}]
+	}
+}
+
+parameter_types! {
+	pub const OperationalFeeMultiplier: u8 = 5;
+}
+
+impl pallet_transaction_payment::Config for Runtime {
+	type OnChargeTransaction = CurrencyAdapter<Balances, ()>;
+	type TransactionByteFee = TransactionByteFee;
+	type WeightToFee = WeightToFee;
+	type FeeMultiplierUpdate = ();
+	type OperationalFeeMultiplier = OperationalFeeMultiplier;
+}
+
+parameter_types! {
+	pub const AssetDeposit: u64 = 2;
+	pub const MetadataDeposit: u64 = 0;
+	pub const StringLimit: u32 = 20;
+}
+
+impl pallet_assets::Config for Runtime {
+	type Event = Event;
+	type Balance = Balance;
+	type AssetId = u32;
+	type Currency = Balances;
+	type ForceOrigin = EnsureRoot<AccountId>;
+	type AssetDeposit = AssetDeposit;
+	type MetadataDepositBase = MetadataDeposit;
+	type MetadataDepositPerByte = MetadataDeposit;
+	type ApprovalDeposit = MetadataDeposit;
+	type StringLimit = StringLimit;
+	type Freezer = ();
+	type Extra = ();
+	type WeightInfo = ();
+}
+
+pub struct HardcodedAuthor;
+const BLOCK_AUTHOR: AccountId = 1234;
+impl FindAuthor<AccountId> for HardcodedAuthor {
+	fn find_author<'a, I>(_: I) -> Option<AccountId>
+	where
+		I: 'a + IntoIterator<Item = (ConsensusEngineId, &'a [u8])>,
+	{
+		Some(BLOCK_AUTHOR)
+	}
+}
+
+impl pallet_authorship::Config for Runtime {
+	type FindAuthor = HardcodedAuthor;
+	type UncleGenerations = ();
+	type FilterUncle = ();
+	type EventHandler = ();
+}
+
+pub struct CreditToBlockAuthor;
+impl HandleCredit<AccountId, Assets> for CreditToBlockAuthor {
+	fn handle_credit(credit: CreditOf<AccountId, Assets>) {
+		let author = pallet_authorship::Pallet::<Runtime>::author();
+		// What to do in case paying the author fails (e.g. because `fee < min_balance`)
+		// default: drop the result which will trigger the `OnDrop` of the imbalance.
+		let _ = <Assets as Balanced<AccountId>>::resolve(&author, credit);
+	}
+}
+
+impl Config for Runtime {
+	type Fungibles = Assets;
+	type OnChargeAssetTransaction = FungiblesAdapter<
+		pallet_assets::BalanceToAssetBalance<Balances, Runtime, ConvertInto>,
+		CreditToBlockAuthor,
+	>;
+}
+
+pub struct ExtBuilder {
+	balance_factor: u64,
+	base_weight: u64,
+	byte_fee: u64,
+	weight_to_fee: u64,
+}
+
+impl Default for ExtBuilder {
+	fn default() -> Self {
+		Self { balance_factor: 1, base_weight: 0, byte_fee: 1, weight_to_fee: 1 }
+	}
+}
+
+impl ExtBuilder {
+	pub fn base_weight(mut self, base_weight: u64) -> Self {
+		self.base_weight = base_weight;
+		self
+	}
+	pub fn balance_factor(mut self, factor: u64) -> Self {
+		self.balance_factor = factor;
+		self
+	}
+	fn set_constants(&self) {
+		EXTRINSIC_BASE_WEIGHT.with(|v| *v.borrow_mut() = self.base_weight);
+		TRANSACTION_BYTE_FEE.with(|v| *v.borrow_mut() = self.byte_fee);
+		WEIGHT_TO_FEE.with(|v| *v.borrow_mut() = self.weight_to_fee);
+	}
+	pub fn build(self) -> sp_io::TestExternalities {
+		self.set_constants();
+		let mut t = frame_system::GenesisConfig::default().build_storage::<Runtime>().unwrap();
+		pallet_balances::GenesisConfig::<Runtime> {
+			balances: if self.balance_factor > 0 {
+				vec![
+					(1, 10 * self.balance_factor),
+					(2, 20 * self.balance_factor),
+					(3, 30 * self.balance_factor),
+					(4, 40 * self.balance_factor),
+					(5, 50 * self.balance_factor),
+					(6, 60 * self.balance_factor),
+				]
+			} else {
+				vec![]
+			},
+		}
+		.assimilate_storage(&mut t)
+		.unwrap();
+		t.into()
+	}
+}
+
+/// create a transaction info struct from weight. Handy to avoid building the whole struct.
+pub fn info_from_weight(w: Weight) -> DispatchInfo {
+	// pays_fee: Pays::Yes -- class: DispatchClass::Normal
+	DispatchInfo { weight: w, ..Default::default() }
+}
+
+fn post_info_from_weight(w: Weight) -> PostDispatchInfo {
+	PostDispatchInfo { actual_weight: Some(w), pays_fee: Default::default() }
+}
+
+fn info_from_pays(p: Pays) -> DispatchInfo {
+	DispatchInfo { pays_fee: p, ..Default::default() }
+}
+
+fn post_info_from_pays(p: Pays) -> PostDispatchInfo {
+	PostDispatchInfo { actual_weight: None, pays_fee: p }
+}
+
+fn default_post_info() -> PostDispatchInfo {
+	PostDispatchInfo { actual_weight: None, pays_fee: Default::default() }
+}
+
+#[test]
+fn transaction_payment_in_native_possible() {
+	let balance_factor = 100;
+	ExtBuilder::default()
+		.balance_factor(balance_factor)
+		.base_weight(5)
+		.build()
+		.execute_with(|| {
+			let len = 10;
+			let pre = ChargeAssetTxPayment::<Runtime>::from(0, None)
+				.pre_dispatch(&1, CALL, &info_from_weight(5), len)
+				.unwrap();
+			let initial_balance = 10 * balance_factor;
+			assert_eq!(Balances::free_balance(1), initial_balance - 5 - 5 - 10);
+
+			assert_ok!(ChargeAssetTxPayment::<Runtime>::post_dispatch(
+				pre,
+				&info_from_weight(5),
+				&default_post_info(),
+				len,
+				&Ok(())
+			));
+			assert_eq!(Balances::free_balance(1), initial_balance - 5 - 5 - 10);
+
+			let pre = ChargeAssetTxPayment::<Runtime>::from(5 /* tipped */, None)
+				.pre_dispatch(&2, CALL, &info_from_weight(100), len)
+				.unwrap();
+			let initial_balance_for_2 = 20 * balance_factor;
+			assert_eq!(Balances::free_balance(2), initial_balance_for_2 - 5 - 10 - 100 - 5);
+
+			assert_ok!(ChargeAssetTxPayment::<Runtime>::post_dispatch(
+				pre,
+				&info_from_weight(100),
+				&post_info_from_weight(50),
+				len,
+				&Ok(())
+			));
+			assert_eq!(Balances::free_balance(2), initial_balance_for_2 - 5 - 10 - 50 - 5);
+		});
+}
+
+#[test]
+fn transaction_payment_in_asset_possible() {
+	let base_weight = 5;
+	let balance_factor = 100;
+	ExtBuilder::default()
+		.balance_factor(balance_factor)
+		.base_weight(base_weight)
+		.build()
+		.execute_with(|| {
+			// create the asset
+			let asset_id = 1;
+			let min_balance = 2;
+			assert_ok!(Assets::force_create(
+				Origin::root(),
+				asset_id,
+				42,   /* owner */
+				true, /* is_sufficient */
+				min_balance
+			));
+
+			// mint into the caller account
+			let caller = 1;
+			let beneficiary = <Runtime as system::Config>::Lookup::unlookup(caller);
+			let balance = 100;
+			assert_ok!(Assets::mint_into(asset_id, &beneficiary, balance));
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+			let weight = 5;
+			let len = 10;
+			// we convert the from weight to fee based on the ratio between asset min balance and
+			// existential deposit
+			let fee = (base_weight + weight + len as u64) * min_balance / ExistentialDeposit::get();
+			let pre = ChargeAssetTxPayment::<Runtime>::from(0, Some(asset_id))
+				.pre_dispatch(&caller, CALL, &info_from_weight(weight), len)
+				.unwrap();
+			// assert that native balance is not used
+			assert_eq!(Balances::free_balance(caller), 10 * balance_factor);
+			// check that fee was charged in the given asset
+			assert_eq!(Assets::balance(asset_id, caller), balance - fee);
+			assert_eq!(Assets::balance(asset_id, BLOCK_AUTHOR), 0);
+
+			assert_ok!(ChargeAssetTxPayment::<Runtime>::post_dispatch(
+				pre,
+				&info_from_weight(weight),
+				&default_post_info(),
+				len,
+				&Ok(())
+			));
+			assert_eq!(Assets::balance(asset_id, caller), balance - fee);
+			// check that the block author gets rewarded
+			assert_eq!(Assets::balance(asset_id, BLOCK_AUTHOR), fee);
+		});
+}
+
+#[test]
+fn transaction_payment_without_fee() {
+	let base_weight = 5;
+	let balance_factor = 100;
+	ExtBuilder::default()
+		.balance_factor(balance_factor)
+		.base_weight(base_weight)
+		.build()
+		.execute_with(|| {
+			// create the asset
+			let asset_id = 1;
+			let min_balance = 2;
+			assert_ok!(Assets::force_create(
+				Origin::root(),
+				asset_id,
+				42,   /* owner */
+				true, /* is_sufficient */
+				min_balance
+			));
+
+			// mint into the caller account
+			let caller = 1;
+			let beneficiary = <Runtime as system::Config>::Lookup::unlookup(caller);
+			let balance = 100;
+			assert_ok!(Assets::mint_into(asset_id, &beneficiary, balance));
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+			let weight = 5;
+			let len = 10;
+			// we convert the from weight to fee based on the ratio between asset min balance and
+			// existential deposit
+			let fee = (base_weight + weight + len as u64) * min_balance / ExistentialDeposit::get();
+			let pre = ChargeAssetTxPayment::<Runtime>::from(0, Some(asset_id))
+				.pre_dispatch(&caller, CALL, &info_from_weight(weight), len)
+				.unwrap();
+			// assert that native balance is not used
+			assert_eq!(Balances::free_balance(caller), 10 * balance_factor);
+			// check that fee was charged in the given asset
+			assert_eq!(Assets::balance(asset_id, caller), balance - fee);
+			assert_eq!(Assets::balance(asset_id, BLOCK_AUTHOR), 0);
+
+			assert_ok!(ChargeAssetTxPayment::<Runtime>::post_dispatch(
+				pre,
+				&info_from_weight(weight),
+				&post_info_from_pays(Pays::No),
+				len,
+				&Ok(())
+			));
+			// caller should be refunded
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+			// check that the block author did not get rewarded
+			assert_eq!(Assets::balance(asset_id, BLOCK_AUTHOR), 0);
+		});
+}
+
+#[test]
+fn asset_transaction_payment_with_tip_and_refund() {
+	let base_weight = 5;
+	ExtBuilder::default()
+		.balance_factor(100)
+		.base_weight(base_weight)
+		.build()
+		.execute_with(|| {
+			// create the asset
+			let asset_id = 1;
+			let min_balance = 2;
+			assert_ok!(Assets::force_create(
+				Origin::root(),
+				asset_id,
+				42,   /* owner */
+				true, /* is_sufficient */
+				min_balance
+			));
+
+			// mint into the caller account
+			let caller = 2;
+			let beneficiary = <Runtime as system::Config>::Lookup::unlookup(caller);
+			let balance = 1000;
+			assert_ok!(Assets::mint_into(asset_id, &beneficiary, balance));
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+			let weight = 100;
+			let tip = 5;
+			let len = 10;
+			// we convert the from weight to fee based on the ratio between asset min balance and
+			// existential deposit
+			let fee_with_tip =
+				(base_weight + weight + len as u64 + tip) * min_balance / ExistentialDeposit::get();
+			let pre = ChargeAssetTxPayment::<Runtime>::from(tip, Some(asset_id))
+				.pre_dispatch(&caller, CALL, &info_from_weight(weight), len)
+				.unwrap();
+			assert_eq!(Assets::balance(asset_id, caller), balance - fee_with_tip);
+
+			let final_weight = 50;
+			assert_ok!(ChargeAssetTxPayment::<Runtime>::post_dispatch(
+				pre,
+				&info_from_weight(weight),
+				&post_info_from_weight(final_weight),
+				len,
+				&Ok(())
+			));
+			let final_fee =
+				fee_with_tip - (weight - final_weight) * min_balance / ExistentialDeposit::get();
+			assert_eq!(Assets::balance(asset_id, caller), balance - (final_fee));
+			assert_eq!(Assets::balance(asset_id, BLOCK_AUTHOR), final_fee);
+		});
+}
+
+#[test]
+fn payment_from_account_with_only_assets() {
+	let base_weight = 5;
+	ExtBuilder::default()
+		.balance_factor(100)
+		.base_weight(base_weight)
+		.build()
+		.execute_with(|| {
+			// create the asset
+			let asset_id = 1;
+			let min_balance = 2;
+			assert_ok!(Assets::force_create(
+				Origin::root(),
+				asset_id,
+				42,   /* owner */
+				true, /* is_sufficient */
+				min_balance
+			));
+
+			// mint into the caller account
+			let caller = 333;
+			let beneficiary = <Runtime as system::Config>::Lookup::unlookup(caller);
+			let balance = 100;
+			assert_ok!(Assets::mint_into(asset_id, &beneficiary, balance));
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+			// assert that native balance is not necessary
+			assert_eq!(Balances::free_balance(caller), 0);
+			let weight = 5;
+			let len = 10;
+			// we convert the from weight to fee based on the ratio between asset min balance and
+			// existential deposit
+			let fee = (base_weight + weight + len as u64) * min_balance / ExistentialDeposit::get();
+			let pre = ChargeAssetTxPayment::<Runtime>::from(0, Some(asset_id))
+				.pre_dispatch(&caller, CALL, &info_from_weight(weight), len)
+				.unwrap();
+			assert_eq!(Balances::free_balance(caller), 0);
+			// check that fee was charged in the given asset
+			assert_eq!(Assets::balance(asset_id, caller), balance - fee);
+
+			assert_ok!(ChargeAssetTxPayment::<Runtime>::post_dispatch(
+				pre,
+				&info_from_weight(weight),
+				&default_post_info(),
+				len,
+				&Ok(())
+			));
+			assert_eq!(Assets::balance(asset_id, caller), balance - fee);
+			assert_eq!(Balances::free_balance(caller), 0);
+		});
+}
+
+#[test]
+fn payment_only_with_existing_sufficient_asset() {
+	let base_weight = 5;
+	ExtBuilder::default()
+		.balance_factor(100)
+		.base_weight(base_weight)
+		.build()
+		.execute_with(|| {
+			let asset_id = 1;
+			let caller = 1;
+			let weight = 5;
+			let len = 10;
+			// pre_dispatch fails for non-existent asset
+			assert!(ChargeAssetTxPayment::<Runtime>::from(0, Some(asset_id))
+				.pre_dispatch(&caller, CALL, &info_from_weight(weight), len)
+				.is_err());
+
+			// create the non-sufficient asset
+			let min_balance = 2;
+			assert_ok!(Assets::force_create(
+				Origin::root(),
+				asset_id,
+				42,    /* owner */
+				false, /* is_sufficient */
+				min_balance
+			));
+			// pre_dispatch fails for non-sufficient asset
+			assert!(ChargeAssetTxPayment::<Runtime>::from(0, Some(asset_id))
+				.pre_dispatch(&caller, CALL, &info_from_weight(weight), len)
+				.is_err());
+		});
+}
+
+#[test]
+fn converted_fee_is_never_zero_if_input_fee_is_not() {
+	let base_weight = 1;
+	ExtBuilder::default()
+		.balance_factor(100)
+		.base_weight(base_weight)
+		.build()
+		.execute_with(|| {
+			// create the asset
+			let asset_id = 1;
+			let min_balance = 1;
+			assert_ok!(Assets::force_create(
+				Origin::root(),
+				asset_id,
+				42,   /* owner */
+				true, /* is_sufficient */
+				min_balance
+			));
+
+			// mint into the caller account
+			let caller = 333;
+			let beneficiary = <Runtime as system::Config>::Lookup::unlookup(caller);
+			let balance = 100;
+			assert_ok!(Assets::mint_into(asset_id, &beneficiary, balance));
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+			let weight = 1;
+			let len = 1;
+			// we convert the from weight to fee based on the ratio between asset min balance and
+			// existential deposit
+			let fee = (base_weight + weight + len as u64) * min_balance / ExistentialDeposit::get();
+			// naive fee calculation would round down to zero
+			assert_eq!(fee, 0);
+			{
+				let pre = ChargeAssetTxPayment::<Runtime>::from(0, Some(asset_id))
+					.pre_dispatch(&caller, CALL, &info_from_pays(Pays::No), len)
+					.unwrap();
+				// `Pays::No` still implies no fees
+				assert_eq!(Assets::balance(asset_id, caller), balance);
+
+				assert_ok!(ChargeAssetTxPayment::<Runtime>::post_dispatch(
+					pre,
+					&info_from_pays(Pays::No),
+					&post_info_from_pays(Pays::No),
+					len,
+					&Ok(())
+				));
+				assert_eq!(Assets::balance(asset_id, caller), balance);
+			}
+			let pre = ChargeAssetTxPayment::<Runtime>::from(0, Some(asset_id))
+				.pre_dispatch(&caller, CALL, &info_from_weight(weight), len)
+				.unwrap();
+			// check that at least one coin was charged in the given asset
+			assert_eq!(Assets::balance(asset_id, caller), balance - 1);
+
+			assert_ok!(ChargeAssetTxPayment::<Runtime>::post_dispatch(
+				pre,
+				&info_from_weight(weight),
+				&default_post_info(),
+				len,
+				&Ok(())
+			));
+			assert_eq!(Assets::balance(asset_id, caller), balance - 1);
+		});
+}
+
+#[test]
+fn post_dispatch_fee_is_zero_if_pre_dispatch_fee_is_zero() {
+	let base_weight = 1;
+	ExtBuilder::default()
+		.balance_factor(100)
+		.base_weight(base_weight)
+		.build()
+		.execute_with(|| {
+			// create the asset
+			let asset_id = 1;
+			let min_balance = 100;
+			assert_ok!(Assets::force_create(
+				Origin::root(),
+				asset_id,
+				42,   /* owner */
+				true, /* is_sufficient */
+				min_balance
+			));
+
+			// mint into the caller account
+			let caller = 333;
+			let beneficiary = <Runtime as system::Config>::Lookup::unlookup(caller);
+			let balance = 100;
+			assert_ok!(Assets::mint_into(asset_id, &beneficiary, balance));
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+			let weight = 1;
+			let len = 1;
+			// we convert the from weight to fee based on the ratio between asset min balance and
+			// existential deposit
+			let fee = (base_weight + weight + len as u64) * min_balance / ExistentialDeposit::get();
+			// calculated fee is greater than 0
+			assert!(fee > 0);
+			let pre = ChargeAssetTxPayment::<Runtime>::from(0, Some(asset_id))
+				.pre_dispatch(&caller, CALL, &info_from_pays(Pays::No), len)
+				.unwrap();
+			// `Pays::No` implies no pre-dispatch fees
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+			let (_tip, _who, initial_payment) = &pre;
+			let not_paying = match initial_payment {
+				&InitialPayment::Nothing => true,
+				_ => false,
+			};
+			assert!(not_paying, "initial payment should be Nothing if we pass Pays::No");
+
+			// `Pays::Yes` on post-dispatch does not mean we pay (we never charge more than the
+			// initial fee)
+			assert_ok!(ChargeAssetTxPayment::<Runtime>::post_dispatch(
+				pre,
+				&info_from_pays(Pays::No),
+				&post_info_from_pays(Pays::Yes),
+				len,
+				&Ok(())
+			));
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+		});
+}
+
+#[test]
+fn post_dispatch_fee_is_zero_if_unsigned_pre_dispatch_fee_is_zero() {
+	let base_weight = 1;
+	ExtBuilder::default()
+		.balance_factor(100)
+		.base_weight(base_weight)
+		.build()
+		.execute_with(|| {
+			// create the asset
+			let asset_id = 1;
+			let min_balance = 100;
+			assert_ok!(Assets::force_create(
+				Origin::root(),
+				asset_id,
+				42,   /* owner */
+				true, /* is_sufficient */
+				min_balance
+			));
+
+			// mint into the caller account
+			let caller = 333;
+			let beneficiary = <Runtime as system::Config>::Lookup::unlookup(caller);
+			let balance = 100;
+			assert_ok!(Assets::mint_into(asset_id, &beneficiary, balance));
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+			let weight = 1;
+			let len = 1;
+			let pre = ChargeAssetTxPayment::<Runtime>::pre_dispatch_unsigned(
+				CALL,
+				&info_from_weight(weight),
+				len,
+			)
+			.unwrap();
+
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+			let (_tip, _who, initial_payment) = &pre;
+			let not_paying = match initial_payment {
+				&InitialPayment::Nothing => true,
+				_ => false,
+			};
+			assert!(not_paying, "initial payment is Nothing for unsigned extrinsics");
+
+			// `Pays::Yes` on post-dispatch does not mean we pay (we never charge more than the
+			// initial fee)
+			assert_ok!(ChargeAssetTxPayment::<Runtime>::post_dispatch(
+				pre,
+				&info_from_weight(weight),
+				&post_info_from_pays(Pays::Yes),
+				len,
+				&Ok(())
+			));
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+		});
+}