Pay tx fee with assets by using the asset conversion pallet (#14340)

* Pay tx by swapping the assets * Change liquidity structure * Uncomment the event * Update frame/transaction-payment/asset-tx-payment/src/payment.rs Co-authored-by: Squirrel <gilescope@gmail.com> * New approach * Fix bounds * Clearer version * Change IsType with Into and From * Enable event * Check ED + fix the logic * Add temp comments * Rework the refund * Clean up * Improve readability * Getting closer * fix * Use fungible instead of Currency * Test account without ed * Final push * Fixed * Rename to pallet-asset-conversion-tx-payment * Bring back the old pallet * Update versions * Update docs * Update readme * Wrong readme updated * Revert back doc change * Fix import * Fix kitchensink * Fix * One more time.. * Wait pls * Update frame/asset-conversion/src/lib.rs Co-authored-by: Squirrel <gilescope@gmail.com> * Update frame/support/src/traits/tokens/fungibles/regular.rs Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com> * Update docs/comments * Docs improvement * Update frame/transaction-payment/asset-conversion-tx-payment/src/lib.rs Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com> * Update frame/transaction-payment/asset-conversion-tx-payment/src/lib.rs Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com> * Update frame/transaction-payment/asset-conversion-tx-payment/src/lib.rs Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com> * Update frame/transaction-payment/asset-conversion-tx-payment/src/lib.rs Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com> * Update frame/transaction-payment/asset-conversion-tx-payment/src/lib.rs Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com> * Payed -> paid * Docs * Update frame/transaction-payment/asset-conversion-tx-payment/README.md Co-authored-by: Muharem Ismailov <ismailov.m.h@gmail.com> * Rewrite docs * Try to clean the deps * Add debug assert * Return back frame-benchmarking * Update cargo * Update frame/transaction-payment/asset-conversion-tx-payment/src/mock.rs Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com> * Rename * clearer error message * Docs for Pay by Swap (#14445) * docs * better error name * more comments * more docs on swap trait * Fix compile errors * Another fix * Refactoring * Update frame/transaction-payment/asset-conversion-tx-payment/src/payment.rs Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com> * Emit an error if we fail to swap the refund back * Add integrity_test * Update frame/asset-conversion/src/lib.rs Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com> * Fmt * Use defensive_ok_or * child PR: Tidy swap event (#14441) * Dedup raising swap event * use expect rather than unwrap * Additional checks for future defence. * cargo fmt * Update frame/asset-conversion/src/lib.rs Co-authored-by: Jegor Sidorenko <5252494+jsidorenko@users.noreply.github.com> --------- Co-authored-by: Jegor Sidorenko <5252494+jsidorenko@users.noreply.github.com> --------- Co-authored-by: Squirrel <gilescope@gmail.com> Co-authored-by: joe petrowski <25483142+joepetrowski@users.noreply.github.com> Co-authored-by: Muharem Ismailov <ismailov.m.h@gmail.com> Co-authored-by: Kian Paimani <5588131+kianenigma@users.noreply.github.com>
2026-06-19 03:01:02 +00:00 · 2023-06-23 21:17:52 +02:00
parent 3e2c73dfad
commit be7c654c42
21 changed files with 1803 additions and 85 deletions
@@ -0,0 +1,708 @@
+// 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.
+
+use super::*;
+
+use frame_support::{
+	assert_ok,
+	dispatch::{DispatchInfo, PostDispatchInfo},
+	pallet_prelude::*,
+	traits::{fungible::Inspect, fungibles::Mutate},
+	weights::Weight,
+};
+use frame_system as system;
+use mock::{ExtrinsicBaseWeight, *};
+use pallet_asset_conversion::NativeOrAssetId;
+use pallet_balances::Call as BalancesCall;
+use sp_runtime::traits::StaticLookup;
+
+const CALL: &<Runtime as frame_system::Config>::RuntimeCall =
+	&RuntimeCall::Balances(BalancesCall::transfer_allow_death { dest: 2, value: 69 });
+
+pub struct ExtBuilder {
+	balance_factor: u64,
+	base_weight: Weight,
+	byte_fee: u64,
+	weight_to_fee: u64,
+}
+
+impl Default for ExtBuilder {
+	fn default() -> Self {
+		Self {
+			balance_factor: 1,
+			base_weight: Weight::from_parts(0, 0),
+			byte_fee: 1,
+			weight_to_fee: 1,
+		}
+	}
+}
+
+impl ExtBuilder {
+	pub fn base_weight(mut self, base_weight: Weight) -> 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) {
+		ExtrinsicBaseWeight::mutate(|v| *v = 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() }
+}
+
+fn setup_lp(asset_id: u32, balance_factor: u64) {
+	let lp_provider = 5;
+	assert_ok!(Balances::force_set_balance(
+		RuntimeOrigin::root(),
+		lp_provider,
+		10_000 * balance_factor
+	));
+	let lp_provider_account = <Runtime as system::Config>::Lookup::unlookup(lp_provider);
+	assert_ok!(Assets::mint_into(asset_id.into(), &lp_provider_account, 10_000 * balance_factor));
+
+	let token_1 = NativeOrAssetId::Native;
+	let token_2 = NativeOrAssetId::Asset(asset_id);
+	assert_ok!(AssetConversion::create_pool(RuntimeOrigin::signed(lp_provider), token_1, token_2));
+
+	assert_ok!(AssetConversion::add_liquidity(
+		RuntimeOrigin::signed(lp_provider),
+		token_1,
+		token_2,
+		1_000 * balance_factor,  // 1 desired
+		10_000 * balance_factor, // 2 desired
+		1,                       // 1 min
+		1,                       // 2 min
+		lp_provider_account,
+	));
+}
+
+const WEIGHT_5: Weight = Weight::from_parts(5, 0);
+const WEIGHT_50: Weight = Weight::from_parts(50, 0);
+const WEIGHT_100: Weight = Weight::from_parts(100, 0);
+
+#[test]
+fn transaction_payment_in_native_possible() {
+	let base_weight = 5;
+	let balance_factor = 100;
+	ExtBuilder::default()
+		.balance_factor(balance_factor)
+		.base_weight(Weight::from_parts(base_weight, 0))
+		.build()
+		.execute_with(|| {
+			let len = 10;
+			let pre = ChargeAssetTxPayment::<Runtime>::from(0, None)
+				.pre_dispatch(&1, CALL, &info_from_weight(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(
+				Some(pre),
+				&info_from_weight(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(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(
+				Some(pre),
+				&info_from_weight(WEIGHT_100),
+				&post_info_from_weight(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(Weight::from_parts(base_weight, 0))
+		.build()
+		.execute_with(|| {
+			// create the asset
+			let asset_id = 1;
+			let min_balance = 2;
+			assert_ok!(Assets::force_create(
+				RuntimeOrigin::root(),
+				asset_id.into(),
+				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 = 1000;
+
+			assert_ok!(Assets::mint_into(asset_id.into(), &beneficiary, balance));
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+
+			let len = 10;
+			let tx_weight = 5;
+
+			setup_lp(asset_id, balance_factor);
+
+			let fee_in_native = base_weight + tx_weight + len as u64;
+			let input_quote = AssetConversion::quote_price_tokens_for_exact_tokens(
+				NativeOrAssetId::Asset(asset_id),
+				NativeOrAssetId::Native,
+				fee_in_native,
+				true,
+			);
+			assert_eq!(input_quote, Some(201));
+
+			let fee_in_asset = input_quote.unwrap();
+			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_5), 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_in_asset);
+
+			assert_ok!(ChargeAssetTxPayment::<Runtime>::post_dispatch(
+				Some(pre),
+				&info_from_weight(WEIGHT_5), // estimated tx weight
+				&default_post_info(),        // weight actually used == estimated
+				len,
+				&Ok(())
+			));
+
+			assert_eq!(Assets::balance(asset_id, caller), balance - fee_in_asset);
+			assert_eq!(TipUnbalancedAmount::get(), 0);
+			assert_eq!(FeeUnbalancedAmount::get(), fee_in_native);
+		});
+}
+
+#[test]
+fn transaction_payment_in_asset_fails_if_no_pool_for_that_asset() {
+	let base_weight = 5;
+	let balance_factor = 100;
+	ExtBuilder::default()
+		.balance_factor(balance_factor)
+		.base_weight(Weight::from_parts(base_weight, 0))
+		.build()
+		.execute_with(|| {
+			// create the asset
+			let asset_id = 1;
+			let min_balance = 2;
+			assert_ok!(Assets::force_create(
+				RuntimeOrigin::root(),
+				asset_id.into(),
+				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 = 1000;
+
+			assert_ok!(Assets::mint_into(asset_id.into(), &beneficiary, balance));
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+
+			let len = 10;
+			let pre = ChargeAssetTxPayment::<Runtime>::from(0, Some(asset_id)).pre_dispatch(
+				&caller,
+				CALL,
+				&info_from_weight(WEIGHT_5),
+				len,
+			);
+
+			// As there is no pool in the dex set up for this asset, conversion should fail.
+			assert!(pre.is_err());
+		});
+}
+
+#[test]
+fn transaction_payment_without_fee() {
+	let base_weight = 5;
+	let balance_factor = 100;
+	ExtBuilder::default()
+		.balance_factor(balance_factor)
+		.base_weight(Weight::from_parts(base_weight, 0))
+		.build()
+		.execute_with(|| {
+			let caller = 1;
+
+			// create the asset
+			let asset_id = 1;
+			let balance = 1000;
+			let min_balance = 2;
+
+			assert_ok!(Assets::force_create(
+				RuntimeOrigin::root(),
+				asset_id.into(),
+				42,   /* owner */
+				true, /* is_sufficient */
+				min_balance,
+			));
+
+			setup_lp(asset_id, balance_factor);
+
+			// mint into the caller account
+			let beneficiary = <Runtime as system::Config>::Lookup::unlookup(caller);
+			assert_ok!(Assets::mint_into(asset_id.into(), &beneficiary, balance));
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+
+			let weight = 5;
+			let len = 10;
+			let fee_in_native = base_weight + weight + len as u64;
+			let input_quote = AssetConversion::quote_price_tokens_for_exact_tokens(
+				NativeOrAssetId::Asset(asset_id),
+				NativeOrAssetId::Native,
+				fee_in_native,
+				true,
+			);
+			assert_eq!(input_quote, Some(201));
+
+			let fee_in_asset = input_quote.unwrap();
+			let pre = ChargeAssetTxPayment::<Runtime>::from(0, Some(asset_id))
+				.pre_dispatch(&caller, CALL, &info_from_weight(WEIGHT_5), 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_in_asset);
+
+			let refund = AssetConversion::quote_price_exact_tokens_for_tokens(
+				NativeOrAssetId::Native,
+				NativeOrAssetId::Asset(asset_id),
+				fee_in_native,
+				true,
+			)
+			.unwrap();
+			assert_eq!(refund, 199);
+
+			assert_ok!(ChargeAssetTxPayment::<Runtime>::post_dispatch(
+				Some(pre),
+				&info_from_weight(WEIGHT_5),
+				&post_info_from_pays(Pays::No),
+				len,
+				&Ok(())
+			));
+
+			// caller should get refunded
+			assert_eq!(Assets::balance(asset_id, caller), balance - fee_in_asset + refund);
+			assert_eq!(Balances::free_balance(caller), 10 * balance_factor);
+		});
+}
+
+#[test]
+fn asset_transaction_payment_with_tip_and_refund() {
+	let base_weight = 5;
+	let balance_factor = 100;
+	ExtBuilder::default()
+		.balance_factor(balance_factor)
+		.base_weight(Weight::from_parts(base_weight, 0))
+		.build()
+		.execute_with(|| {
+			// create the asset
+			let asset_id = 1;
+			let min_balance = 2;
+			assert_ok!(Assets::force_create(
+				RuntimeOrigin::root(),
+				asset_id.into(),
+				42,   /* owner */
+				true, /* is_sufficient */
+				min_balance,
+			));
+
+			setup_lp(asset_id, balance_factor);
+
+			// mint into the caller account
+			let caller = 2;
+			let beneficiary = <Runtime as system::Config>::Lookup::unlookup(caller);
+			let balance = 10000;
+
+			assert_ok!(Assets::mint_into(asset_id.into(), &beneficiary, balance));
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+
+			let weight = 100;
+			let tip = 5;
+			let len = 10;
+			let fee_in_native = base_weight + weight + len as u64 + tip;
+			let input_quote = AssetConversion::quote_price_tokens_for_exact_tokens(
+				NativeOrAssetId::Asset(asset_id),
+				NativeOrAssetId::Native,
+				fee_in_native,
+				true,
+			);
+			assert_eq!(input_quote, Some(1206));
+
+			let fee_in_asset = input_quote.unwrap();
+			let pre = ChargeAssetTxPayment::<Runtime>::from(tip, Some(asset_id))
+				.pre_dispatch(&caller, CALL, &info_from_weight(WEIGHT_100), len)
+				.unwrap();
+			assert_eq!(Assets::balance(asset_id, caller), balance - fee_in_asset);
+
+			let final_weight = 50;
+			let expected_fee = fee_in_native - final_weight - tip;
+			let expected_token_refund = AssetConversion::quote_price_exact_tokens_for_tokens(
+				NativeOrAssetId::Native,
+				NativeOrAssetId::Asset(asset_id),
+				fee_in_native - expected_fee - tip,
+				true,
+			)
+			.unwrap();
+
+			assert_ok!(ChargeAssetTxPayment::<Runtime>::post_dispatch(
+				Some(pre),
+				&info_from_weight(WEIGHT_100),
+				&post_info_from_weight(WEIGHT_50),
+				len,
+				&Ok(())
+			));
+
+			assert_eq!(TipUnbalancedAmount::get(), tip);
+			assert_eq!(FeeUnbalancedAmount::get(), expected_fee);
+
+			// caller should get refunded
+			assert_eq!(
+				Assets::balance(asset_id, caller),
+				balance - fee_in_asset + expected_token_refund
+			);
+			assert_eq!(Balances::free_balance(caller), 20 * balance_factor);
+		});
+}
+
+#[test]
+fn payment_from_account_with_only_assets() {
+	let base_weight = 5;
+	let balance_factor = 100;
+	ExtBuilder::default()
+		.balance_factor(balance_factor)
+		.base_weight(Weight::from_parts(base_weight, 0))
+		.build()
+		.execute_with(|| {
+			// create the asset
+			let asset_id = 1;
+			let min_balance = 2;
+			assert_ok!(Assets::force_create(
+				RuntimeOrigin::root(),
+				asset_id.into(),
+				42,   /* owner */
+				true, /* is_sufficient */
+				min_balance,
+			));
+
+			setup_lp(asset_id, balance_factor);
+
+			// mint into the caller account
+			let caller = 333;
+			let beneficiary = <Runtime as system::Config>::Lookup::unlookup(caller);
+			let balance = 1000;
+
+			assert_ok!(Assets::mint_into(asset_id.into(), &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;
+
+			let fee_in_native = base_weight + weight + len as u64;
+			let ed = Balances::minimum_balance();
+			let fee_in_asset = AssetConversion::quote_price_tokens_for_exact_tokens(
+				NativeOrAssetId::Asset(asset_id),
+				NativeOrAssetId::Native,
+				fee_in_native + ed,
+				true,
+			)
+			.unwrap();
+			assert_eq!(fee_in_asset, 301);
+
+			let pre = ChargeAssetTxPayment::<Runtime>::from(0, Some(asset_id))
+				.pre_dispatch(&caller, CALL, &info_from_weight(WEIGHT_5), len)
+				.unwrap();
+			assert_eq!(Balances::free_balance(caller), ed);
+			// check that fee was charged in the given asset
+			assert_eq!(Assets::balance(asset_id, caller), balance - fee_in_asset);
+
+			let refund = AssetConversion::quote_price_exact_tokens_for_tokens(
+				NativeOrAssetId::Native,
+				NativeOrAssetId::Asset(asset_id),
+				ed,
+				true,
+			)
+			.unwrap();
+
+			assert_ok!(ChargeAssetTxPayment::<Runtime>::post_dispatch(
+				Some(pre),
+				&info_from_weight(WEIGHT_5),
+				&default_post_info(),
+				len,
+				&Ok(())
+			));
+			assert_eq!(Assets::balance(asset_id, caller), balance - fee_in_asset + refund);
+			assert_eq!(Balances::free_balance(caller), 0);
+
+			assert_eq!(TipUnbalancedAmount::get(), 0);
+			assert_eq!(FeeUnbalancedAmount::get(), fee_in_native);
+		});
+}
+
+#[test]
+fn converted_fee_is_never_zero_if_input_fee_is_not() {
+	let base_weight = 1;
+	let balance_factor = 100;
+	ExtBuilder::default()
+		.balance_factor(balance_factor)
+		.base_weight(Weight::from_parts(base_weight, 0))
+		.build()
+		.execute_with(|| {
+			// create the asset
+			let asset_id = 1;
+			let min_balance = 1;
+			assert_ok!(Assets::force_create(
+				RuntimeOrigin::root(),
+				asset_id.into(),
+				42,   /* owner */
+				true, /* is_sufficient */
+				min_balance
+			));
+
+			setup_lp(asset_id, balance_factor);
+
+			// 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.into(), &beneficiary, balance));
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+
+			let weight = 1;
+			let len = 1;
+
+			// there will be no conversion when the fee is zero
+			{
+				let pre = ChargeAssetTxPayment::<Runtime>::from(0, Some(asset_id))
+					.pre_dispatch(&caller, CALL, &info_from_pays(Pays::No), len)
+					.unwrap();
+				// `Pays::No` implies there are no fees
+				assert_eq!(Assets::balance(asset_id, caller), balance);
+
+				assert_ok!(ChargeAssetTxPayment::<Runtime>::post_dispatch(
+					Some(pre),
+					&info_from_pays(Pays::No),
+					&post_info_from_pays(Pays::No),
+					len,
+					&Ok(())
+				));
+				assert_eq!(Assets::balance(asset_id, caller), balance);
+			}
+
+			// validate even a small fee gets converted to asset.
+			let fee_in_native = base_weight + weight + len as u64;
+			let fee_in_asset = AssetConversion::quote_price_tokens_for_exact_tokens(
+				NativeOrAssetId::Asset(asset_id),
+				NativeOrAssetId::Native,
+				fee_in_native,
+				true,
+			)
+			.unwrap();
+
+			let pre = ChargeAssetTxPayment::<Runtime>::from(0, Some(asset_id))
+				.pre_dispatch(&caller, CALL, &info_from_weight(Weight::from_parts(weight, 0)), len)
+				.unwrap();
+			assert_eq!(Assets::balance(asset_id, caller), balance - fee_in_asset);
+
+			assert_ok!(ChargeAssetTxPayment::<Runtime>::post_dispatch(
+				Some(pre),
+				&info_from_weight(Weight::from_parts(weight, 0)),
+				&default_post_info(),
+				len,
+				&Ok(())
+			));
+			assert_eq!(Assets::balance(asset_id, caller), balance - fee_in_asset);
+		});
+}
+
+#[test]
+fn post_dispatch_fee_is_zero_if_pre_dispatch_fee_is_zero() {
+	let base_weight = 1;
+	ExtBuilder::default()
+		.balance_factor(100)
+		.base_weight(Weight::from_parts(base_weight, 0))
+		.build()
+		.execute_with(|| {
+			// create the asset
+			let asset_id = 1;
+			let min_balance = 100;
+			assert_ok!(Assets::force_create(
+				RuntimeOrigin::root(),
+				asset_id.into(),
+				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 = 1000;
+
+			assert_ok!(Assets::mint_into(asset_id.into(), &beneficiary, balance));
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+
+			let weight = 1;
+			let len = 1;
+			let fee = base_weight + weight + len as u64;
+
+			// 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, _asset_id) = &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(
+				Some(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(Weight::from_parts(base_weight, 0))
+		.build()
+		.execute_with(|| {
+			// create the asset
+			let asset_id = 1;
+			let min_balance = 100;
+			assert_ok!(Assets::force_create(
+				RuntimeOrigin::root(),
+				asset_id.into(),
+				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 = 1000;
+
+			assert_ok!(Assets::mint_into(asset_id.into(), &beneficiary, balance));
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+
+			let weight = 1;
+			let len = 1;
+			ChargeAssetTxPayment::<Runtime>::pre_dispatch_unsigned(
+				CALL,
+				&info_from_weight(Weight::from_parts(weight, 0)),
+				len,
+			)
+			.unwrap();
+
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+
+			// `Pays::Yes` on post-dispatch does not mean we pay (we never charge more than the
+			// initial fee)
+			assert_ok!(ChargeAssetTxPayment::<Runtime>::post_dispatch(
+				None,
+				&info_from_weight(Weight::from_parts(weight, 0)),
+				&post_info_from_pays(Pays::Yes),
+				len,
+				&Ok(())
+			));
+			assert_eq!(Assets::balance(asset_id, caller), balance);
+		});
+}