feat: Rebrand Polkadot/Substrate references to PezkuwiChain

This commit systematically rebrands various references from Parity Technologies'
Polkadot/Substrate ecosystem to PezkuwiChain within the kurdistan-sdk.

Key changes include:
- Updated external repository URLs (zombienet-sdk, parity-db, parity-scale-codec, wasm-instrument) to point to pezkuwichain forks.
- Modified internal documentation and code comments to reflect PezkuwiChain naming and structure.
- Replaced direct references to  with  or specific paths within the  for XCM, Pezkuwi, and other modules.
- Cleaned up deprecated  issue and PR references in various  and  files, particularly in  and  modules.
- Adjusted image and logo URLs in documentation to point to PezkuwiChain assets.
- Removed or rephrased comments related to external Polkadot/Substrate PRs and issues.

This is a significant step towards fully customizing the SDK for the PezkuwiChain ecosystem.

pezcumulus/primitives/utility/src/lib.rs

@@ -0,0 +1,906 @@
+// Copyright (C) Parity Technologies (UK) Ltd.
+// This file is part of Pezcumulus.
+// 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.
+
+//! Helper datatypes for pezcumulus. This includes the [`ParentAsUmp`] routing type which will route
+//! messages into an [`UpwardMessageSender`] if the destination is `Parent`.
+
+#![cfg_attr(not(feature = "std"), no_std)]
+
+extern crate alloc;
+
+use alloc::{vec, vec::Vec};
+use codec::Encode;
+use core::marker::PhantomData;
+use cumulus_primitives_core::{MessageSendError, UpwardMessageSender};
+use pezframe_support::{
+	defensive,
+	traits::{tokens::fungibles, Get, OnUnbalanced as OnUnbalancedT},
+	weights::{Weight, WeightToFee as WeightToFeeT},
+	CloneNoBound,
+};
+use pezpallet_asset_conversion::SwapCredit as SwapCreditT;
+use pezkuwi_runtime_common::xcm_sender::PriceForMessageDelivery;
+use pezsp_runtime::{
+	traits::{Saturating, Zero},
+	SaturatedConversion,
+};
+use xcm::{latest::prelude::*, VersionedLocation, VersionedXcm, WrapVersion};
+use xcm_builder::{InspectMessageQueues, TakeRevenue};
+use xcm_executor::{
+	traits::{MatchesFungibles, TransactAsset, WeightTrader},
+	AssetsInHolding,
+};
+
+#[cfg(test)]
+mod tests;
+
+/// Xcm router which recognises the `Parent` destination and handles it by sending the message into
+/// the given UMP `UpwardMessageSender` implementation. Thus this essentially adapts an
+/// `UpwardMessageSender` trait impl into a `SendXcm` trait impl.
+///
+/// NOTE: This is a pretty dumb "just send it" router; we will probably want to introduce queuing
+/// to UMP eventually and when we do, the pallet which implements the queuing will be responsible
+/// for the `SendXcm` implementation.
+pub struct ParentAsUmp<T, W, P>(PhantomData<(T, W, P)>);
+impl<T, W, P> SendXcm for ParentAsUmp<T, W, P>
+where
+	T: UpwardMessageSender,
+	W: WrapVersion,
+	P: PriceForMessageDelivery<Id = ()>,
+{
+	type Ticket = Vec<u8>;
+
+	fn validate(dest: &mut Option<Location>, msg: &mut Option<Xcm<()>>) -> SendResult<Vec<u8>> {
+		let d = dest.take().ok_or(SendError::MissingArgument)?;
+
+		if d.contains_parents_only(1) {
+			// An upward message for the relay chain.
+			let xcm = msg.take().ok_or(SendError::MissingArgument)?;
+			let price = P::price_for_delivery((), &xcm);
+			let versioned_xcm =
+				W::wrap_version(&d, xcm).map_err(|()| SendError::DestinationUnsupported)?;
+			versioned_xcm
+				.check_is_decodable()
+				.map_err(|()| SendError::ExceedsMaxMessageSize)?;
+			let data = versioned_xcm.encode();
+
+			// Pre-check with our message sender if everything else is okay.
+			T::can_send_upward_message(&data).map_err(Self::map_upward_sender_err)?;
+
+			Ok((data, price))
+		} else {
+			// Anything else is unhandled. This includes a message that is not meant for us.
+			// We need to make sure that dest/msg is not consumed here.
+			*dest = Some(d);
+			Err(SendError::NotApplicable)
+		}
+	}
+
+	fn deliver(data: Vec<u8>) -> Result<XcmHash, SendError> {
+		let (_, hash) = T::send_upward_message(data).map_err(Self::map_upward_sender_err)?;
+		Ok(hash)
+	}
+
+	#[cfg(feature = "runtime-benchmarks")]
+	fn ensure_successful_delivery(location: Option<Location>) {
+		if location.as_ref().map_or(false, |l| l.contains_parents_only(1)) {
+			T::ensure_successful_delivery();
+		}
+	}
+}
+
+impl<T, W, P> ParentAsUmp<T, W, P> {
+	fn map_upward_sender_err(message_send_error: MessageSendError) -> SendError {
+		match message_send_error {
+			MessageSendError::TooBig => SendError::ExceedsMaxMessageSize,
+			e => SendError::Transport(e.into()),
+		}
+	}
+}
+
+impl<T: UpwardMessageSender + InspectMessageQueues, W, P> InspectMessageQueues
+	for ParentAsUmp<T, W, P>
+{
+	fn clear_messages() {
+		T::clear_messages();
+	}
+
+	fn get_messages() -> Vec<(VersionedLocation, Vec<VersionedXcm<()>>)> {
+		T::get_messages()
+	}
+}
+
+/// Contains information to handle refund/payment for xcm-execution
+#[derive(Clone, Eq, PartialEq, Debug)]
+struct AssetTraderRefunder {
+	// The amount of weight bought minus the weigh already refunded
+	weight_outstanding: Weight,
+	// The concrete asset containing the asset location and outstanding balance
+	outstanding_concrete_asset: Asset,
+}
+
+/// Charges for execution in the first asset of those selected for fee payment
+/// Only succeeds for Concrete Fungible Assets
+/// First tries to convert the this Asset into a local assetId
+/// Then charges for this assetId as described by FeeCharger
+/// Weight, paid balance, local asset Id and the location is stored for
+/// later refund purposes
+/// Important: Errors if the Trader is being called twice by 2 BuyExecution instructions
+/// Alternatively we could just return payment in the aforementioned case
+#[derive(CloneNoBound)]
+pub struct TakeFirstAssetTrader<
+	AccountId: Eq,
+	FeeCharger: ChargeWeightInFungibles<AccountId, ConcreteAssets>,
+	Matcher: MatchesFungibles<ConcreteAssets::AssetId, ConcreteAssets::Balance>,
+	ConcreteAssets: fungibles::Mutate<AccountId> + fungibles::Balanced<AccountId>,
+	HandleRefund: TakeRevenue,
+>(
+	Option<AssetTraderRefunder>,
+	PhantomData<(AccountId, FeeCharger, Matcher, ConcreteAssets, HandleRefund)>,
+);
+impl<
+		AccountId: Eq,
+		FeeCharger: ChargeWeightInFungibles<AccountId, ConcreteAssets>,
+		Matcher: MatchesFungibles<ConcreteAssets::AssetId, ConcreteAssets::Balance>,
+		ConcreteAssets: fungibles::Mutate<AccountId> + fungibles::Balanced<AccountId>,
+		HandleRefund: TakeRevenue,
+	> WeightTrader
+	for TakeFirstAssetTrader<AccountId, FeeCharger, Matcher, ConcreteAssets, HandleRefund>
+{
+	fn new() -> Self {
+		Self(None, PhantomData)
+	}
+	// We take first asset
+	// Check whether we can convert fee to asset_fee (is_sufficient, min_deposit)
+	// If everything goes well, we charge.
+	fn buy_weight(
+		&mut self,
+		weight: Weight,
+		payment: xcm_executor::AssetsInHolding,
+		context: &XcmContext,
+	) -> Result<xcm_executor::AssetsInHolding, XcmError> {
+		log::trace!(target: "xcm::weight", "TakeFirstAssetTrader::buy_weight weight: {:?}, payment: {:?}, context: {:?}", weight, payment, context);
+
+		// Make sure we don't enter twice
+		if self.0.is_some() {
+			return Err(XcmError::NotWithdrawable);
+		}
+
+		// We take the very first asset from payment
+		// (assets are sorted by fungibility/amount after this conversion)
+		let assets: Assets = payment.clone().into();
+
+		// Take the first asset from the selected Assets
+		let first = assets.get(0).ok_or(XcmError::AssetNotFound)?;
+
+		// Get the local asset id in which we can pay for fees
+		let (local_asset_id, _) =
+			Matcher::matches_fungibles(first).map_err(|_| XcmError::AssetNotFound)?;
+
+		// Calculate how much we should charge in the asset_id for such amount of weight
+		// Require at least a payment of minimum_balance
+		// Necessary for fully collateral-backed assets
+		let asset_balance: u128 =
+			FeeCharger::charge_weight_in_fungibles(local_asset_id.clone(), weight)
+				.map(|amount| {
+					let minimum_balance = ConcreteAssets::minimum_balance(local_asset_id);
+					if amount < minimum_balance {
+						minimum_balance
+					} else {
+						amount
+					}
+				})?
+				.try_into()
+				.map_err(|_| XcmError::Overflow)?;
+
+		// Convert to the same kind of asset, with the required fungible balance
+		let required = first.id.clone().into_asset(asset_balance.into());
+
+		// Subtract payment
+		let unused = payment.checked_sub(required.clone()).map_err(|_| XcmError::TooExpensive)?;
+
+		// record weight and asset
+		self.0 = Some(AssetTraderRefunder {
+			weight_outstanding: weight,
+			outstanding_concrete_asset: required,
+		});
+
+		Ok(unused)
+	}
+
+	fn refund_weight(&mut self, weight: Weight, context: &XcmContext) -> Option<Asset> {
+		log::trace!(target: "xcm::weight", "TakeFirstAssetTrader::refund_weight weight: {:?}, context: {:?}", weight, context);
+		if let Some(AssetTraderRefunder {
+			mut weight_outstanding,
+			outstanding_concrete_asset: Asset { id, fun },
+		}) = self.0.clone()
+		{
+			// Get the local asset id in which we can refund fees
+			let (local_asset_id, outstanding_balance) =
+				Matcher::matches_fungibles(&(id.clone(), fun).into()).ok()?;
+
+			let minimum_balance = ConcreteAssets::minimum_balance(local_asset_id.clone());
+
+			// Calculate asset_balance
+			// This read should have already be cached in buy_weight
+			let (asset_balance, outstanding_minus_subtracted) =
+				FeeCharger::charge_weight_in_fungibles(local_asset_id, weight).ok().map(
+					|asset_balance| {
+						// Require at least a drop of minimum_balance
+						// Necessary for fully collateral-backed assets
+						if outstanding_balance.saturating_sub(asset_balance) > minimum_balance {
+							(asset_balance, outstanding_balance.saturating_sub(asset_balance))
+						}
+						// If the amount to be refunded leaves the remaining balance below ED,
+						// we just refund the exact amount that guarantees at least ED will be
+						// dropped
+						else {
+							(outstanding_balance.saturating_sub(minimum_balance), minimum_balance)
+						}
+					},
+				)?;
+
+			// Convert balances into u128
+			let outstanding_minus_subtracted: u128 = outstanding_minus_subtracted.saturated_into();
+			let asset_balance: u128 = asset_balance.saturated_into();
+
+			// Construct outstanding_concrete_asset with the same location id and subtracted
+			// balance
+			let outstanding_concrete_asset: Asset =
+				(id.clone(), outstanding_minus_subtracted).into();
+
+			// Subtract from existing weight and balance
+			weight_outstanding = weight_outstanding.saturating_sub(weight);
+
+			// Override AssetTraderRefunder
+			self.0 = Some(AssetTraderRefunder { weight_outstanding, outstanding_concrete_asset });
+
+			// Only refund if positive
+			if asset_balance > 0 {
+				Some((id, asset_balance).into())
+			} else {
+				None
+			}
+		} else {
+			None
+		}
+	}
+}
+
+impl<
+		AccountId: Eq,
+		FeeCharger: ChargeWeightInFungibles<AccountId, ConcreteAssets>,
+		Matcher: MatchesFungibles<ConcreteAssets::AssetId, ConcreteAssets::Balance>,
+		ConcreteAssets: fungibles::Mutate<AccountId> + fungibles::Balanced<AccountId>,
+		HandleRefund: TakeRevenue,
+	> Drop for TakeFirstAssetTrader<AccountId, FeeCharger, Matcher, ConcreteAssets, HandleRefund>
+{
+	fn drop(&mut self) {
+		if let Some(asset_trader) = self.0.clone() {
+			HandleRefund::take_revenue(asset_trader.outstanding_concrete_asset);
+		}
+	}
+}
+
+/// XCM fee depositor to which we implement the `TakeRevenue` trait.
+/// It receives a `Transact` implemented argument and a 32 byte convertible `AccountId`, and the fee
+/// receiver account's `FungiblesMutateAdapter` should be identical to that implemented by
+/// `WithdrawAsset`.
+pub struct XcmFeesTo32ByteAccount<FungiblesMutateAdapter, AccountId, ReceiverAccount>(
+	PhantomData<(FungiblesMutateAdapter, AccountId, ReceiverAccount)>,
+);
+impl<
+		FungiblesMutateAdapter: TransactAsset,
+		AccountId: Clone + Into<[u8; 32]>,
+		ReceiverAccount: Get<Option<AccountId>>,
+	> TakeRevenue for XcmFeesTo32ByteAccount<FungiblesMutateAdapter, AccountId, ReceiverAccount>
+{
+	fn take_revenue(revenue: Asset) {
+		if let Some(receiver) = ReceiverAccount::get() {
+			let ok = FungiblesMutateAdapter::deposit_asset(
+				&revenue,
+				&([AccountId32 { network: None, id: receiver.into() }].into()),
+				None,
+			)
+			.is_ok();
+
+			debug_assert!(ok, "`deposit_asset` cannot generally fail; qed");
+		}
+	}
+}
+
+/// ChargeWeightInFungibles trait, which converts a given amount of weight
+/// and an assetId, and it returns the balance amount that should be charged
+/// in such assetId for that amount of weight
+pub trait ChargeWeightInFungibles<AccountId, Assets: fungibles::Inspect<AccountId>> {
+	fn charge_weight_in_fungibles(
+		asset_id: <Assets as fungibles::Inspect<AccountId>>::AssetId,
+		weight: Weight,
+	) -> Result<<Assets as fungibles::Inspect<AccountId>>::Balance, XcmError>;
+}
+
+/// Provides an implementation of [`WeightTrader`] to charge for weight using the first asset
+/// specified in the `payment` argument.
+///
+/// The asset used to pay for the weight must differ from the `Target` asset and be exchangeable for
+/// the same `Target` asset through `SwapCredit`.
+///
+/// ### Parameters:
+/// - `Target`: the asset into which the user's payment will be exchanged using `SwapCredit`.
+/// - `SwapCredit`: mechanism used for the exchange of the user's payment asset into the `Target`.
+/// - `WeightToFee`: weight to the `Target` asset fee calculator.
+/// - `Fungibles`: registry of fungible assets.
+/// - `FungiblesAssetMatcher`: utility for mapping [`Asset`] to `Fungibles::AssetId` and
+///   `Fungibles::Balance`.
+/// - `OnUnbalanced`: handler for the fee payment.
+/// - `AccountId`: the account identifier type.
+pub struct SwapFirstAssetTrader<
+	Target: Get<Fungibles::AssetId>,
+	SwapCredit: SwapCreditT<
+		AccountId,
+		Balance = Fungibles::Balance,
+		AssetKind = Fungibles::AssetId,
+		Credit = fungibles::Credit<AccountId, Fungibles>,
+	>,
+	WeightToFee: WeightToFeeT<Balance = Fungibles::Balance>,
+	Fungibles: fungibles::Balanced<AccountId>,
+	FungiblesAssetMatcher: MatchesFungibles<Fungibles::AssetId, Fungibles::Balance>,
+	OnUnbalanced: OnUnbalancedT<fungibles::Credit<AccountId, Fungibles>>,
+	AccountId,
+> where
+	Fungibles::Balance: Into<u128>,
+{
+	/// Accumulated fee paid for XCM execution.
+	total_fee: fungibles::Credit<AccountId, Fungibles>,
+	/// Last asset utilized by a client to settle a fee.
+	last_fee_asset: Option<AssetId>,
+	_phantom_data: PhantomData<(
+		Target,
+		SwapCredit,
+		WeightToFee,
+		Fungibles,
+		FungiblesAssetMatcher,
+		OnUnbalanced,
+		AccountId,
+	)>,
+}
+
+impl<
+		Target: Get<Fungibles::AssetId>,
+		SwapCredit: SwapCreditT<
+			AccountId,
+			Balance = Fungibles::Balance,
+			AssetKind = Fungibles::AssetId,
+			Credit = fungibles::Credit<AccountId, Fungibles>,
+		>,
+		WeightToFee: WeightToFeeT<Balance = Fungibles::Balance>,
+		Fungibles: fungibles::Balanced<AccountId>,
+		FungiblesAssetMatcher: MatchesFungibles<Fungibles::AssetId, Fungibles::Balance>,
+		OnUnbalanced: OnUnbalancedT<fungibles::Credit<AccountId, Fungibles>>,
+		AccountId,
+	> WeightTrader
+	for SwapFirstAssetTrader<
+		Target,
+		SwapCredit,
+		WeightToFee,
+		Fungibles,
+		FungiblesAssetMatcher,
+		OnUnbalanced,
+		AccountId,
+	>
+where
+	Fungibles::Balance: Into<u128>,
+{
+	fn new() -> Self {
+		Self {
+			total_fee: fungibles::Credit::<AccountId, Fungibles>::zero(Target::get()),
+			last_fee_asset: None,
+			_phantom_data: PhantomData,
+		}
+	}
+
+	fn buy_weight(
+		&mut self,
+		weight: Weight,
+		mut payment: AssetsInHolding,
+		_context: &XcmContext,
+	) -> Result<AssetsInHolding, XcmError> {
+		log::trace!(
+			target: "xcm::weight",
+			"SwapFirstAssetTrader::buy_weight weight: {:?}, payment: {:?}",
+			weight,
+			payment,
+		);
+		let first_asset: Asset =
+			payment.fungible.pop_first().ok_or(XcmError::AssetNotFound)?.into();
+		let (fungibles_asset, balance) = FungiblesAssetMatcher::matches_fungibles(&first_asset)
+			.map_err(|error| {
+				log::trace!(
+					target: "xcm::weight",
+					"SwapFirstAssetTrader::buy_weight asset {:?} didn't match. Error: {:?}",
+					first_asset,
+					error,
+				);
+				XcmError::AssetNotFound
+			})?;
+
+		let swap_asset = fungibles_asset.clone().into();
+		if Target::get().eq(&swap_asset) {
+			log::trace!(
+				target: "xcm::weight",
+				"SwapFirstAssetTrader::buy_weight Asset was same as Target, swap not needed.",
+			);
+			// current trader is not applicable.
+			return Err(XcmError::FeesNotMet);
+		}
+
+		let credit_in = Fungibles::issue(fungibles_asset, balance);
+		let fee = WeightToFee::weight_to_fee(&weight);
+
+		// swap the user's asset for the `Target` asset.
+		let (credit_out, credit_change) = SwapCredit::swap_tokens_for_exact_tokens(
+			vec![swap_asset, Target::get()],
+			credit_in,
+			fee,
+		)
+		.map_err(|(credit_in, error)| {
+			log::trace!(
+				target: "xcm::weight",
+				"SwapFirstAssetTrader::buy_weight swap couldn't be done. Error was: {:?}",
+				error,
+			);
+			drop(credit_in);
+			XcmError::FeesNotMet
+		})?;
+
+		match self.total_fee.subsume(credit_out) {
+			Err(credit_out) => {
+				// error may occur if `total_fee.asset` differs from `credit_out.asset`, which does
+				// not apply in this context.
+				defensive!(
+					"`total_fee.asset` must be equal to `credit_out.asset`",
+					(self.total_fee.asset(), credit_out.asset())
+				);
+				return Err(XcmError::FeesNotMet);
+			},
+			_ => (),
+		};
+		self.last_fee_asset = Some(first_asset.id.clone());
+
+		payment.fungible.insert(first_asset.id, credit_change.peek().into());
+		drop(credit_change);
+		Ok(payment)
+	}
+
+	fn refund_weight(&mut self, weight: Weight, _context: &XcmContext) -> Option<Asset> {
+		log::trace!(
+			target: "xcm::weight",
+			"SwapFirstAssetTrader::refund_weight weight: {:?}, self.total_fee: {:?}",
+			weight,
+			self.total_fee,
+		);
+		if self.total_fee.peek().is_zero() {
+			// noting yet paid to refund.
+			return None;
+		}
+		let mut refund_asset = if let Some(asset) = &self.last_fee_asset {
+			// create an initial zero refund in the asset used in the last `buy_weight`.
+			(asset.clone(), Fungible(0)).into()
+		} else {
+			return None;
+		};
+		let refund_amount = WeightToFee::weight_to_fee(&weight);
+		if refund_amount >= self.total_fee.peek() {
+			// not enough was paid to refund the `weight`.
+			return None;
+		}
+
+		let refund_swap_asset = FungiblesAssetMatcher::matches_fungibles(&refund_asset)
+			.map(|(a, _)| a.into())
+			.ok()?;
+
+		let refund = self.total_fee.extract(refund_amount);
+		let refund = match SwapCredit::swap_exact_tokens_for_tokens(
+			vec![Target::get(), refund_swap_asset],
+			refund,
+			None,
+		) {
+			Ok(refund_in_target) => refund_in_target,
+			Err((refund, _)) => {
+				// return an attempted refund back to the `total_fee`.
+				let _ = self.total_fee.subsume(refund).map_err(|refund| {
+					// error may occur if `total_fee.asset` differs from `refund.asset`, which does
+					// not apply in this context.
+					defensive!(
+						"`total_fee.asset` must be equal to `refund.asset`",
+						(self.total_fee.asset(), refund.asset())
+					);
+				});
+				return None;
+			},
+		};
+
+		refund_asset.fun = refund.peek().into().into();
+		drop(refund);
+		Some(refund_asset)
+	}
+}
+
+impl<
+		Target: Get<Fungibles::AssetId>,
+		SwapCredit: SwapCreditT<
+			AccountId,
+			Balance = Fungibles::Balance,
+			AssetKind = Fungibles::AssetId,
+			Credit = fungibles::Credit<AccountId, Fungibles>,
+		>,
+		WeightToFee: WeightToFeeT<Balance = Fungibles::Balance>,
+		Fungibles: fungibles::Balanced<AccountId>,
+		FungiblesAssetMatcher: MatchesFungibles<Fungibles::AssetId, Fungibles::Balance>,
+		OnUnbalanced: OnUnbalancedT<fungibles::Credit<AccountId, Fungibles>>,
+		AccountId,
+	> Drop
+	for SwapFirstAssetTrader<
+		Target,
+		SwapCredit,
+		WeightToFee,
+		Fungibles,
+		FungiblesAssetMatcher,
+		OnUnbalanced,
+		AccountId,
+	>
+where
+	Fungibles::Balance: Into<u128>,
+{
+	fn drop(&mut self) {
+		if self.total_fee.peek().is_zero() {
+			return;
+		}
+		let total_fee = self.total_fee.extract(self.total_fee.peek());
+		OnUnbalanced::on_unbalanced(total_fee);
+	}
+}
+
+#[cfg(test)]
+mod test_xcm_router {
+	use super::*;
+	use cumulus_primitives_core::UpwardMessage;
+	use pezframe_support::assert_ok;
+	use xcm::MAX_XCM_DECODE_DEPTH;
+
+	/// Validates [`validate`] for required Some(destination) and Some(message)
+	struct OkFixedXcmHashWithAssertingRequiredInputsSender;
+	impl OkFixedXcmHashWithAssertingRequiredInputsSender {
+		const FIXED_XCM_HASH: [u8; 32] = [9; 32];
+
+		fn fixed_delivery_asset() -> Assets {
+			Assets::new()
+		}
+
+		fn expected_delivery_result() -> Result<(XcmHash, Assets), SendError> {
+			Ok((Self::FIXED_XCM_HASH, Self::fixed_delivery_asset()))
+		}
+	}
+	impl SendXcm for OkFixedXcmHashWithAssertingRequiredInputsSender {
+		type Ticket = ();
+
+		fn validate(
+			destination: &mut Option<Location>,
+			message: &mut Option<Xcm<()>>,
+		) -> SendResult<Self::Ticket> {
+			assert!(destination.is_some());
+			assert!(message.is_some());
+			Ok(((), OkFixedXcmHashWithAssertingRequiredInputsSender::fixed_delivery_asset()))
+		}
+
+		fn deliver(_: Self::Ticket) -> Result<XcmHash, SendError> {
+			Ok(Self::FIXED_XCM_HASH)
+		}
+	}
+
+	/// Impl [`UpwardMessageSender`] that return `Ok` for `can_send_upward_message`.
+	struct CanSendUpwardMessageSender;
+	impl UpwardMessageSender for CanSendUpwardMessageSender {
+		fn send_upward_message(_: UpwardMessage) -> Result<(u32, XcmHash), MessageSendError> {
+			Err(MessageSendError::Other)
+		}
+
+		fn can_send_upward_message(_: &UpwardMessage) -> Result<(), MessageSendError> {
+			Ok(())
+		}
+	}
+
+	#[test]
+	fn parent_as_ump_does_not_consume_dest_or_msg_on_not_applicable() {
+		// dummy message
+		let message = Xcm(vec![Trap(5)]);
+
+		// ParentAsUmp - check dest is really not applicable
+		let dest = (Parent, Parent, Parent);
+		let mut dest_wrapper = Some(dest.into());
+		let mut msg_wrapper = Some(message.clone());
+		assert_eq!(
+			Err(SendError::NotApplicable),
+			<ParentAsUmp<(), (), ()> as SendXcm>::validate(&mut dest_wrapper, &mut msg_wrapper)
+		);
+
+		// check wrapper were not consumed
+		assert_eq!(Some(dest.into()), dest_wrapper.take());
+		assert_eq!(Some(message.clone()), msg_wrapper.take());
+
+		// another try with router chain with asserting sender
+		assert_eq!(
+			OkFixedXcmHashWithAssertingRequiredInputsSender::expected_delivery_result(),
+			send_xcm::<(ParentAsUmp<(), (), ()>, OkFixedXcmHashWithAssertingRequiredInputsSender)>(
+				dest.into(),
+				message
+			)
+		);
+	}
+
+	#[test]
+	fn parent_as_ump_consumes_dest_and_msg_on_ok_validate() {
+		// dummy message
+		let message = Xcm(vec![Trap(5)]);
+
+		// ParentAsUmp - check dest/msg is valid
+		let dest = (Parent, Here);
+		let mut dest_wrapper = Some(dest.clone().into());
+		let mut msg_wrapper = Some(message.clone());
+		assert!(<ParentAsUmp<CanSendUpwardMessageSender, (), ()> as SendXcm>::validate(
+			&mut dest_wrapper,
+			&mut msg_wrapper
+		)
+		.is_ok());
+
+		// check wrapper were consumed
+		assert_eq!(None, dest_wrapper.take());
+		assert_eq!(None, msg_wrapper.take());
+
+		// another try with router chain with asserting sender
+		assert_eq!(
+			Err(SendError::Transport("Other")),
+			send_xcm::<(
+				ParentAsUmp<CanSendUpwardMessageSender, (), ()>,
+				OkFixedXcmHashWithAssertingRequiredInputsSender
+			)>(dest.into(), message)
+		);
+	}
+
+	#[test]
+	fn parent_as_ump_validate_nested_xcm_works() {
+		let dest = Parent;
+
+		type Router = ParentAsUmp<CanSendUpwardMessageSender, (), ()>;
+
+		// Message that is not too deeply nested:
+		let mut good = Xcm(vec![ClearOrigin]);
+		for _ in 0..MAX_XCM_DECODE_DEPTH - 1 {
+			good = Xcm(vec![SetAppendix(good)]);
+		}
+
+		// Check that the good message is validated:
+		assert_ok!(<Router as SendXcm>::validate(&mut Some(dest.into()), &mut Some(good.clone())));
+
+		// Nesting the message one more time should reject it:
+		let bad = Xcm(vec![SetAppendix(good)]);
+		assert_eq!(
+			Err(SendError::ExceedsMaxMessageSize),
+			<Router as SendXcm>::validate(&mut Some(dest.into()), &mut Some(bad))
+		);
+	}
+}
+#[cfg(test)]
+mod test_trader {
+	use super::*;
+	use pezframe_support::{
+		assert_ok,
+		traits::tokens::{
+			DepositConsequence, Fortitude, Preservation, Provenance, WithdrawConsequence,
+		},
+	};
+	use pezsp_runtime::DispatchError;
+	use xcm_executor::{traits::Error, AssetsInHolding};
+
+	#[test]
+	fn take_first_asset_trader_buy_weight_called_twice_throws_error() {
+		const AMOUNT: u128 = 100;
+
+		// prepare prerequisites to instantiate `TakeFirstAssetTrader`
+		type TestAccountId = u32;
+		type TestAssetId = u32;
+		type TestBalance = u128;
+		struct TestAssets;
+		impl MatchesFungibles<TestAssetId, TestBalance> for TestAssets {
+			fn matches_fungibles(a: &Asset) -> Result<(TestAssetId, TestBalance), Error> {
+				match a {
+					Asset { fun: Fungible(amount), id: AssetId(_id) } => Ok((1, *amount)),
+					_ => Err(Error::AssetNotHandled),
+				}
+			}
+		}
+		impl fungibles::Inspect<TestAccountId> for TestAssets {
+			type AssetId = TestAssetId;
+			type Balance = TestBalance;
+
+			fn total_issuance(_: Self::AssetId) -> Self::Balance {
+				todo!()
+			}
+
+			fn minimum_balance(_: Self::AssetId) -> Self::Balance {
+				0
+			}
+
+			fn balance(_: Self::AssetId, _: &TestAccountId) -> Self::Balance {
+				todo!()
+			}
+
+			fn total_balance(_: Self::AssetId, _: &TestAccountId) -> Self::Balance {
+				todo!()
+			}
+
+			fn reducible_balance(
+				_: Self::AssetId,
+				_: &TestAccountId,
+				_: Preservation,
+				_: Fortitude,
+			) -> Self::Balance {
+				todo!()
+			}
+
+			fn can_deposit(
+				_: Self::AssetId,
+				_: &TestAccountId,
+				_: Self::Balance,
+				_: Provenance,
+			) -> DepositConsequence {
+				todo!()
+			}
+
+			fn can_withdraw(
+				_: Self::AssetId,
+				_: &TestAccountId,
+				_: Self::Balance,
+			) -> WithdrawConsequence<Self::Balance> {
+				todo!()
+			}
+
+			fn asset_exists(_: Self::AssetId) -> bool {
+				todo!()
+			}
+		}
+		impl fungibles::Mutate<TestAccountId> for TestAssets {}
+		impl fungibles::Balanced<TestAccountId> for TestAssets {
+			type OnDropCredit = fungibles::DecreaseIssuance<TestAccountId, Self>;
+			type OnDropDebt = fungibles::IncreaseIssuance<TestAccountId, Self>;
+		}
+		impl fungibles::Unbalanced<TestAccountId> for TestAssets {
+			fn handle_dust(_: fungibles::Dust<TestAccountId, Self>) {
+				todo!()
+			}
+			fn write_balance(
+				_: Self::AssetId,
+				_: &TestAccountId,
+				_: Self::Balance,
+			) -> Result<Option<Self::Balance>, DispatchError> {
+				todo!()
+			}
+
+			fn set_total_issuance(_: Self::AssetId, _: Self::Balance) {
+				todo!()
+			}
+		}
+
+		struct FeeChargerAssetsHandleRefund;
+		impl ChargeWeightInFungibles<TestAccountId, TestAssets> for FeeChargerAssetsHandleRefund {
+			fn charge_weight_in_fungibles(
+				_: <TestAssets as fungibles::Inspect<TestAccountId>>::AssetId,
+				_: Weight,
+			) -> Result<<TestAssets as fungibles::Inspect<TestAccountId>>::Balance, XcmError> {
+				Ok(AMOUNT)
+			}
+		}
+		impl TakeRevenue for FeeChargerAssetsHandleRefund {
+			fn take_revenue(_: Asset) {}
+		}
+
+		// create new instance
+		type Trader = TakeFirstAssetTrader<
+			TestAccountId,
+			FeeChargerAssetsHandleRefund,
+			TestAssets,
+			TestAssets,
+			FeeChargerAssetsHandleRefund,
+		>;
+		let mut trader = <Trader as WeightTrader>::new();
+		let ctx = XcmContext { origin: None, message_id: XcmHash::default(), topic: None };
+
+		// prepare test data
+		let asset: Asset = (Here, AMOUNT).into();
+		let payment = AssetsInHolding::from(asset);
+		let weight_to_buy = Weight::from_parts(1_000, 1_000);
+
+		// lets do first call (success)
+		assert_ok!(trader.buy_weight(weight_to_buy, payment.clone(), &ctx));
+
+		// lets do second call (error)
+		assert_eq!(trader.buy_weight(weight_to_buy, payment, &ctx), Err(XcmError::NotWithdrawable));
+	}
+}
+
+/// Implementation of `xcm_builder::EnsureDelivery` which helps to ensure delivery to the
+/// parent relay chain. Deposits existential deposit for origin (if needed).
+/// Deposits estimated fee to the origin account (if needed).
+/// Allows triggering of additional logic for a specific `ParaId` (e.g. to open an HRMP channel) if
+/// needed.
+#[cfg(feature = "runtime-benchmarks")]
+pub struct ToParentDeliveryHelper<XcmConfig, ExistentialDeposit, PriceForDelivery>(
+	core::marker::PhantomData<(XcmConfig, ExistentialDeposit, PriceForDelivery)>,
+);
+
+#[cfg(feature = "runtime-benchmarks")]
+impl<
+		XcmConfig: xcm_executor::Config,
+		ExistentialDeposit: Get<Option<Asset>>,
+		PriceForDelivery: PriceForMessageDelivery<Id = ()>,
+	> xcm_builder::EnsureDelivery
+	for ToParentDeliveryHelper<XcmConfig, ExistentialDeposit, PriceForDelivery>
+{
+	fn ensure_successful_delivery(
+		origin_ref: &Location,
+		dest: &Location,
+		fee_reason: xcm_executor::traits::FeeReason,
+	) -> (Option<xcm_executor::FeesMode>, Option<Assets>) {
+		use xcm::{latest::MAX_ITEMS_IN_ASSETS, MAX_INSTRUCTIONS_TO_DECODE};
+		use xcm_executor::{traits::FeeManager, FeesMode};
+
+		// check if the destination is relay/parent
+		if dest.ne(&Location::parent()) {
+			return (None, None);
+		}
+
+		// Ensure routers
+		XcmConfig::XcmSender::ensure_successful_delivery(Some(Location::parent()));
+
+		let mut fees_mode = None;
+		if !XcmConfig::FeeManager::is_waived(Some(origin_ref), fee_reason) {
+			// if not waived, we need to set up accounts for paying and receiving fees
+
+			// mint ED to origin if needed
+			if let Some(ed) = ExistentialDeposit::get() {
+				XcmConfig::AssetTransactor::deposit_asset(&ed, &origin_ref, None).unwrap();
+			}
+
+			// overestimate delivery fee
+			let mut max_assets: Vec<Asset> = Vec::new();
+			for i in 0..MAX_ITEMS_IN_ASSETS {
+				max_assets.push((GeneralIndex(i as u128), 100u128).into());
+			}
+			let overestimated_xcm =
+				vec![WithdrawAsset(max_assets.into()); MAX_INSTRUCTIONS_TO_DECODE as usize].into();
+			let overestimated_fees = PriceForDelivery::price_for_delivery((), &overestimated_xcm);
+
+			// mint overestimated fee to origin
+			for fee in overestimated_fees.inner() {
+				XcmConfig::AssetTransactor::deposit_asset(&fee, &origin_ref, None).unwrap();
+			}
+
+			// expected worst case - direct withdraw
+			fees_mode = Some(FeesMode { jit_withdraw: true });
+		}
+		(fees_mode, None)
+	}
+}

pezcumulus/primitives/utility/src/tests/mod.rs

@@ -0,0 +1,17 @@
+// Copyright (C) Parity Technologies (UK) Ltd.
+// This file is part of Pezcumulus.
+// 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.
+
+mod swap_first;

pezcumulus/primitives/utility/src/tests/swap_first.rs

@@ -0,0 +1,551 @@
+// Copyright (C) Parity Technologies (UK) Ltd.
+// This file is part of Pezcumulus.
+// 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 crate::*;
+use pezframe_support::{parameter_types, traits::fungibles::Inspect};
+use mock::{setup_pool, AccountId, AssetId, Balance, Fungibles};
+use xcm::latest::AssetId as XcmAssetId;
+use xcm_executor::AssetsInHolding;
+
+fn create_holding_asset(asset_id: AssetId, amount: Balance) -> AssetsInHolding {
+	create_asset(asset_id, amount).into()
+}
+
+fn create_asset(asset_id: AssetId, amount: Balance) -> Asset {
+	Asset { id: create_asset_id(asset_id), fun: Fungible(amount) }
+}
+
+fn create_asset_id(asset_id: AssetId) -> XcmAssetId {
+	AssetId(Location::new(0, [GeneralIndex(asset_id.into())]))
+}
+
+fn xcm_context() -> XcmContext {
+	XcmContext { origin: None, message_id: [0u8; 32], topic: None }
+}
+
+fn weight_worth_of(fee: Balance) -> Weight {
+	Weight::from_parts(fee.try_into().unwrap(), 0)
+}
+
+const TARGET_ASSET: AssetId = 1;
+const CLIENT_ASSET: AssetId = 2;
+const CLIENT_ASSET_2: AssetId = 3;
+
+parameter_types! {
+	pub const TargetAsset: AssetId = TARGET_ASSET;
+}
+
+pub type Trader = SwapFirstAssetTrader<
+	TargetAsset,
+	mock::Swap,
+	mock::WeightToFee,
+	mock::Fungibles,
+	mock::FungiblesMatcher,
+	(),
+	AccountId,
+>;
+
+#[test]
+fn holding_asset_swap_for_target() {
+	let client_asset_total = 15;
+	let fee = 5;
+
+	setup_pool(CLIENT_ASSET, 1000, TARGET_ASSET, 1000);
+
+	let holding_asset = create_holding_asset(CLIENT_ASSET, client_asset_total);
+	let holding_change = create_holding_asset(CLIENT_ASSET, client_asset_total - fee);
+
+	let target_total = Fungibles::total_issuance(TARGET_ASSET);
+	let client_total = Fungibles::total_issuance(CLIENT_ASSET);
+
+	let mut trader = Trader::new();
+	assert_eq!(
+		trader.buy_weight(weight_worth_of(fee), holding_asset, &xcm_context()).unwrap(),
+		holding_change
+	);
+
+	assert_eq!(trader.total_fee.peek(), fee);
+	assert_eq!(trader.last_fee_asset, Some(create_asset_id(CLIENT_ASSET)));
+
+	assert_eq!(Fungibles::total_issuance(TARGET_ASSET), target_total);
+	assert_eq!(Fungibles::total_issuance(CLIENT_ASSET), client_total + fee);
+}
+
+#[test]
+fn holding_asset_swap_for_target_twice() {
+	let client_asset_total = 20;
+	let fee1 = 5;
+	let fee2 = 6;
+
+	setup_pool(CLIENT_ASSET, 1000, TARGET_ASSET, 1000);
+
+	let holding_asset = create_holding_asset(CLIENT_ASSET, client_asset_total);
+	let holding_change1 = create_holding_asset(CLIENT_ASSET, client_asset_total - fee1);
+	let holding_change2 = create_holding_asset(CLIENT_ASSET, client_asset_total - fee1 - fee2);
+
+	let target_total = Fungibles::total_issuance(TARGET_ASSET);
+	let client_total = Fungibles::total_issuance(CLIENT_ASSET);
+
+	let mut trader = Trader::new();
+	assert_eq!(
+		trader.buy_weight(weight_worth_of(fee1), holding_asset, &xcm_context()).unwrap(),
+		holding_change1
+	);
+	assert_eq!(
+		trader
+			.buy_weight(weight_worth_of(fee2), holding_change1, &xcm_context())
+			.unwrap(),
+		holding_change2
+	);
+
+	assert_eq!(trader.total_fee.peek(), fee1 + fee2);
+	assert_eq!(trader.last_fee_asset, Some(create_asset_id(CLIENT_ASSET)));
+
+	assert_eq!(Fungibles::total_issuance(TARGET_ASSET), target_total);
+	assert_eq!(Fungibles::total_issuance(CLIENT_ASSET), client_total + fee1 + fee2);
+}
+
+#[test]
+fn buy_and_refund_twice_for_target() {
+	let client_asset_total = 15;
+	let fee = 5;
+	let refund1 = 4;
+	let refund2 = 2;
+
+	setup_pool(CLIENT_ASSET, 1000, TARGET_ASSET, 1000);
+	// create pool for refund swap.
+	setup_pool(TARGET_ASSET, 1000, CLIENT_ASSET, 1000);
+
+	let holding_asset = create_holding_asset(CLIENT_ASSET, client_asset_total);
+	let holding_change = create_holding_asset(CLIENT_ASSET, client_asset_total - fee);
+	let refund_asset = create_asset(CLIENT_ASSET, refund1);
+
+	let target_total = Fungibles::total_issuance(TARGET_ASSET);
+	let client_total = Fungibles::total_issuance(CLIENT_ASSET);
+
+	let mut trader = Trader::new();
+	assert_eq!(
+		trader.buy_weight(weight_worth_of(fee), holding_asset, &xcm_context()).unwrap(),
+		holding_change
+	);
+
+	assert_eq!(trader.total_fee.peek(), fee);
+	assert_eq!(trader.last_fee_asset, Some(create_asset_id(CLIENT_ASSET)));
+
+	assert_eq!(trader.refund_weight(weight_worth_of(refund1), &xcm_context()), Some(refund_asset));
+
+	assert_eq!(trader.total_fee.peek(), fee - refund1);
+	assert_eq!(trader.last_fee_asset, Some(create_asset_id(CLIENT_ASSET)));
+
+	assert_eq!(trader.refund_weight(weight_worth_of(refund2), &xcm_context()), None);
+
+	assert_eq!(trader.total_fee.peek(), fee - refund1);
+	assert_eq!(trader.last_fee_asset, Some(create_asset_id(CLIENT_ASSET)));
+
+	assert_eq!(Fungibles::total_issuance(TARGET_ASSET), target_total);
+	assert_eq!(Fungibles::total_issuance(CLIENT_ASSET), client_total + fee - refund1);
+}
+
+#[test]
+fn buy_with_various_assets_and_refund_for_target() {
+	let client_asset_total = 10;
+	let client_asset_2_total = 15;
+	let fee1 = 5;
+	let fee2 = 6;
+	let refund1 = 6;
+	let refund2 = 4;
+
+	setup_pool(CLIENT_ASSET, 1000, TARGET_ASSET, 1000);
+	setup_pool(CLIENT_ASSET_2, 1000, TARGET_ASSET, 1000);
+	// create pool for refund swap.
+	setup_pool(TARGET_ASSET, 1000, CLIENT_ASSET_2, 1000);
+
+	let holding_asset = create_holding_asset(CLIENT_ASSET, client_asset_total);
+	let holding_asset_2 = create_holding_asset(CLIENT_ASSET_2, client_asset_2_total);
+	let holding_change = create_holding_asset(CLIENT_ASSET, client_asset_total - fee1);
+	let holding_change_2 = create_holding_asset(CLIENT_ASSET_2, client_asset_2_total - fee2);
+	// both refunds in the latest buy asset (`CLIENT_ASSET_2`).
+	let refund_asset = create_asset(CLIENT_ASSET_2, refund1);
+	let refund_asset_2 = create_asset(CLIENT_ASSET_2, refund2);
+
+	let target_total = Fungibles::total_issuance(TARGET_ASSET);
+	let client_total = Fungibles::total_issuance(CLIENT_ASSET);
+	let client_total_2 = Fungibles::total_issuance(CLIENT_ASSET_2);
+
+	let mut trader = Trader::new();
+	// first purchase with `CLIENT_ASSET`.
+	assert_eq!(
+		trader.buy_weight(weight_worth_of(fee1), holding_asset, &xcm_context()).unwrap(),
+		holding_change
+	);
+
+	assert_eq!(trader.total_fee.peek(), fee1);
+	assert_eq!(trader.last_fee_asset, Some(create_asset_id(CLIENT_ASSET)));
+
+	// second purchase with `CLIENT_ASSET_2`.
+	assert_eq!(
+		trader
+			.buy_weight(weight_worth_of(fee2), holding_asset_2, &xcm_context())
+			.unwrap(),
+		holding_change_2
+	);
+
+	assert_eq!(trader.total_fee.peek(), fee1 + fee2);
+	assert_eq!(trader.last_fee_asset, Some(create_asset_id(CLIENT_ASSET_2)));
+
+	// first refund in the last asset used with `buy_weight`.
+	assert_eq!(trader.refund_weight(weight_worth_of(refund1), &xcm_context()), Some(refund_asset));
+
+	assert_eq!(trader.total_fee.peek(), fee1 + fee2 - refund1);
+	assert_eq!(trader.last_fee_asset, Some(create_asset_id(CLIENT_ASSET_2)));
+
+	// second refund in the last asset used with `buy_weight`.
+	assert_eq!(
+		trader.refund_weight(weight_worth_of(refund2), &xcm_context()),
+		Some(refund_asset_2)
+	);
+
+	assert_eq!(trader.total_fee.peek(), fee1 + fee2 - refund1 - refund2);
+	assert_eq!(trader.last_fee_asset, Some(create_asset_id(CLIENT_ASSET_2)));
+
+	assert_eq!(Fungibles::total_issuance(TARGET_ASSET), target_total);
+	assert_eq!(Fungibles::total_issuance(CLIENT_ASSET), client_total + fee1);
+	assert_eq!(
+		Fungibles::total_issuance(CLIENT_ASSET_2),
+		client_total_2 + fee2 - refund1 - refund2
+	);
+}
+
+#[test]
+fn not_enough_to_refund() {
+	let client_asset_total = 15;
+	let fee = 5;
+	let refund = 6;
+
+	setup_pool(CLIENT_ASSET, 1000, TARGET_ASSET, 1000);
+
+	let holding_asset = create_holding_asset(CLIENT_ASSET, client_asset_total);
+	let holding_change = create_holding_asset(CLIENT_ASSET, client_asset_total - fee);
+
+	let target_total = Fungibles::total_issuance(TARGET_ASSET);
+	let client_total = Fungibles::total_issuance(CLIENT_ASSET);
+
+	let mut trader = Trader::new();
+	assert_eq!(
+		trader.buy_weight(weight_worth_of(fee), holding_asset, &xcm_context()).unwrap(),
+		holding_change
+	);
+
+	assert_eq!(trader.total_fee.peek(), fee);
+	assert_eq!(trader.last_fee_asset, Some(create_asset_id(CLIENT_ASSET)));
+
+	assert_eq!(trader.refund_weight(weight_worth_of(refund), &xcm_context()), None);
+
+	assert_eq!(Fungibles::total_issuance(TARGET_ASSET), target_total);
+	assert_eq!(Fungibles::total_issuance(CLIENT_ASSET), client_total + fee);
+}
+
+#[test]
+fn not_exchangeable_to_refund() {
+	let client_asset_total = 15;
+	let fee = 5;
+	let refund = 1;
+
+	setup_pool(CLIENT_ASSET, 1000, TARGET_ASSET, 1000);
+
+	let holding_asset = create_holding_asset(CLIENT_ASSET, client_asset_total);
+	let holding_change = create_holding_asset(CLIENT_ASSET, client_asset_total - fee);
+
+	let target_total = Fungibles::total_issuance(TARGET_ASSET);
+	let client_total = Fungibles::total_issuance(CLIENT_ASSET);
+
+	let mut trader = Trader::new();
+	assert_eq!(
+		trader.buy_weight(weight_worth_of(fee), holding_asset, &xcm_context()).unwrap(),
+		holding_change
+	);
+
+	assert_eq!(trader.total_fee.peek(), fee);
+	assert_eq!(trader.last_fee_asset, Some(create_asset_id(CLIENT_ASSET)));
+
+	assert_eq!(trader.refund_weight(weight_worth_of(refund), &xcm_context()), None);
+
+	assert_eq!(Fungibles::total_issuance(TARGET_ASSET), target_total);
+	assert_eq!(Fungibles::total_issuance(CLIENT_ASSET), client_total + fee);
+}
+
+#[test]
+fn nothing_to_refund() {
+	let fee = 5;
+
+	let mut trader = Trader::new();
+	assert_eq!(trader.refund_weight(weight_worth_of(fee), &xcm_context()), None);
+}
+
+#[test]
+fn holding_asset_not_exchangeable_for_target() {
+	let holding_asset = create_holding_asset(CLIENT_ASSET, 10);
+
+	let target_total = Fungibles::total_issuance(TARGET_ASSET);
+	let client_total = Fungibles::total_issuance(CLIENT_ASSET);
+
+	let mut trader = Trader::new();
+	assert_eq!(
+		trader
+			.buy_weight(Weight::from_all(10), holding_asset, &xcm_context())
+			.unwrap_err(),
+		XcmError::FeesNotMet
+	);
+
+	assert_eq!(Fungibles::total_issuance(TARGET_ASSET), target_total);
+	assert_eq!(Fungibles::total_issuance(CLIENT_ASSET), client_total);
+}
+
+#[test]
+fn empty_holding_asset() {
+	let mut trader = Trader::new();
+	assert_eq!(
+		trader
+			.buy_weight(Weight::from_all(10), AssetsInHolding::new(), &xcm_context())
+			.unwrap_err(),
+		XcmError::AssetNotFound
+	);
+}
+
+#[test]
+fn fails_to_match_holding_asset() {
+	let mut trader = Trader::new();
+	let holding_asset = Asset { id: AssetId(Location::new(1, [Teyrchain(1)])), fun: Fungible(10) };
+	assert_eq!(
+		trader
+			.buy_weight(Weight::from_all(10), holding_asset.into(), &xcm_context())
+			.unwrap_err(),
+		XcmError::AssetNotFound
+	);
+}
+
+#[test]
+fn holding_asset_equal_to_target_asset() {
+	let mut trader = Trader::new();
+	let holding_asset = create_holding_asset(TargetAsset::get(), 10);
+	assert_eq!(
+		trader
+			.buy_weight(Weight::from_all(10), holding_asset, &xcm_context())
+			.unwrap_err(),
+		XcmError::FeesNotMet
+	);
+}
+
+pub mod mock {
+	use crate::*;
+	use core::cell::RefCell;
+	use pezframe_support::{
+		ensure,
+		traits::{
+			fungibles::{Balanced, DecreaseIssuance, Dust, IncreaseIssuance, Inspect, Unbalanced},
+			tokens::{
+				DepositConsequence, Fortitude, Fortitude::Polite, Precision::Exact, Preservation,
+				Preservation::Preserve, Provenance, WithdrawConsequence,
+			},
+		},
+	};
+	use pezsp_runtime::{traits::One, DispatchError};
+	use std::collections::HashMap;
+	use xcm::latest::Junction;
+
+	pub type AccountId = u64;
+	pub type AssetId = u32;
+	pub type Balance = u128;
+	pub type Credit = fungibles::Credit<AccountId, Fungibles>;
+
+	thread_local! {
+	   pub static TOTAL_ISSUANCE: RefCell<HashMap<AssetId, Balance>> = RefCell::new(HashMap::new());
+	   pub static ACCOUNT: RefCell<HashMap<(AssetId, AccountId), Balance>> = RefCell::new(HashMap::new());
+	   pub static SWAP: RefCell<HashMap<(AssetId, AssetId), AccountId>> = RefCell::new(HashMap::new());
+	}
+
+	pub struct Swap {}
+	impl SwapCreditT<AccountId> for Swap {
+		type Balance = Balance;
+		type AssetKind = AssetId;
+		type Credit = Credit;
+		fn max_path_len() -> u32 {
+			2
+		}
+		fn swap_exact_tokens_for_tokens(
+			path: Vec<Self::AssetKind>,
+			credit_in: Self::Credit,
+			amount_out_min: Option<Self::Balance>,
+		) -> Result<Self::Credit, (Self::Credit, DispatchError)> {
+			ensure!(2 == path.len(), (credit_in, DispatchError::Unavailable));
+			ensure!(
+				credit_in.peek() >= amount_out_min.unwrap_or(Self::Balance::zero()),
+				(credit_in, DispatchError::Unavailable)
+			);
+			let swap_res = SWAP.with(|b| b.borrow().get(&(path[0], path[1])).map(|v| *v));
+			let pool_account = match swap_res {
+				Some(a) => a,
+				None => return Err((credit_in, DispatchError::Unavailable)),
+			};
+			let credit_out = match Fungibles::withdraw(
+				path[1],
+				&pool_account,
+				credit_in.peek(),
+				Exact,
+				Preserve,
+				Polite,
+			) {
+				Ok(c) => c,
+				Err(_) => return Err((credit_in, DispatchError::Unavailable)),
+			};
+			Fungibles::resolve(&pool_account, credit_in)
+				.map_err(|c| (c, DispatchError::Unavailable))?;
+			Ok(credit_out)
+		}
+		fn swap_tokens_for_exact_tokens(
+			path: Vec<Self::AssetKind>,
+			credit_in: Self::Credit,
+			amount_out: Self::Balance,
+		) -> Result<(Self::Credit, Self::Credit), (Self::Credit, DispatchError)> {
+			ensure!(2 == path.len(), (credit_in, DispatchError::Unavailable));
+			ensure!(credit_in.peek() >= amount_out, (credit_in, DispatchError::Unavailable));
+			let swap_res = SWAP.with(|b| b.borrow().get(&(path[0], path[1])).map(|v| *v));
+			let pool_account = match swap_res {
+				Some(a) => a,
+				None => return Err((credit_in, DispatchError::Unavailable)),
+			};
+			let credit_out = match Fungibles::withdraw(
+				path[1],
+				&pool_account,
+				amount_out,
+				Exact,
+				Preserve,
+				Polite,
+			) {
+				Ok(c) => c,
+				Err(_) => return Err((credit_in, DispatchError::Unavailable)),
+			};
+			let (credit_in, change) = credit_in.split(amount_out);
+			Fungibles::resolve(&pool_account, credit_in)
+				.map_err(|c| (c, DispatchError::Unavailable))?;
+			Ok((credit_out, change))
+		}
+	}
+
+	pub fn pool_account(asset1: AssetId, asset2: AssetId) -> AccountId {
+		(1000 + asset1 * 10 + asset2 * 100).into()
+	}
+
+	pub fn setup_pool(asset1: AssetId, liquidity1: Balance, asset2: AssetId, liquidity2: Balance) {
+		let account = pool_account(asset1, asset2);
+		SWAP.with(|b| b.borrow_mut().insert((asset1, asset2), account));
+		let debt1 = Fungibles::deposit(asset1, &account, liquidity1, Exact);
+		let debt2 = Fungibles::deposit(asset2, &account, liquidity2, Exact);
+		drop(debt1);
+		drop(debt2);
+	}
+
+	pub struct WeightToFee;
+	impl WeightToFeeT for WeightToFee {
+		type Balance = Balance;
+		fn weight_to_fee(weight: &Weight) -> Self::Balance {
+			(weight.ref_time() + weight.proof_size()).into()
+		}
+	}
+
+	pub struct Fungibles {}
+	impl Inspect<AccountId> for Fungibles {
+		type AssetId = AssetId;
+		type Balance = Balance;
+		fn total_issuance(asset: Self::AssetId) -> Self::Balance {
+			TOTAL_ISSUANCE.with(|b| b.borrow().get(&asset).map_or(Self::Balance::zero(), |b| *b))
+		}
+		fn minimum_balance(_: Self::AssetId) -> Self::Balance {
+			Self::Balance::one()
+		}
+		fn total_balance(asset: Self::AssetId, who: &AccountId) -> Self::Balance {
+			ACCOUNT.with(|b| b.borrow().get(&(asset, *who)).map_or(Self::Balance::zero(), |b| *b))
+		}
+		fn balance(asset: Self::AssetId, who: &AccountId) -> Self::Balance {
+			ACCOUNT.with(|b| b.borrow().get(&(asset, *who)).map_or(Self::Balance::zero(), |b| *b))
+		}
+		fn reducible_balance(
+			asset: Self::AssetId,
+			who: &AccountId,
+			_: Preservation,
+			_: Fortitude,
+		) -> Self::Balance {
+			ACCOUNT.with(|b| b.borrow().get(&(asset, *who)).map_or(Self::Balance::zero(), |b| *b))
+		}
+		fn can_deposit(
+			_: Self::AssetId,
+			_: &AccountId,
+			_: Self::Balance,
+			_: Provenance,
+		) -> DepositConsequence {
+			unimplemented!()
+		}
+		fn can_withdraw(
+			_: Self::AssetId,
+			_: &AccountId,
+			_: Self::Balance,
+		) -> WithdrawConsequence<Self::Balance> {
+			unimplemented!()
+		}
+		fn asset_exists(_: Self::AssetId) -> bool {
+			unimplemented!()
+		}
+	}
+
+	impl Unbalanced<AccountId> for Fungibles {
+		fn set_total_issuance(asset: Self::AssetId, amount: Self::Balance) {
+			TOTAL_ISSUANCE.with(|b| b.borrow_mut().insert(asset, amount));
+		}
+		fn handle_dust(_: Dust<AccountId, Self>) {
+			unimplemented!()
+		}
+		fn write_balance(
+			asset: Self::AssetId,
+			who: &AccountId,
+			amount: Self::Balance,
+		) -> Result<Option<Self::Balance>, DispatchError> {
+			let _ = ACCOUNT.with(|b| b.borrow_mut().insert((asset, *who), amount));
+			Ok(None)
+		}
+	}
+
+	impl Balanced<AccountId> for Fungibles {
+		type OnDropCredit = DecreaseIssuance<AccountId, Self>;
+		type OnDropDebt = IncreaseIssuance<AccountId, Self>;
+	}
+
+	pub struct FungiblesMatcher;
+	impl MatchesFungibles<AssetId, Balance> for FungiblesMatcher {
+		fn matches_fungibles(
+			a: &Asset,
+		) -> core::result::Result<(AssetId, Balance), xcm_executor::traits::Error> {
+			match a {
+				Asset { fun: Fungible(amount), id: AssetId(inner_location) } =>
+					match inner_location.unpack() {
+						(0, [Junction::GeneralIndex(id)]) =>
+							Ok(((*id).try_into().unwrap(), *amount)),
+						_ => Err(xcm_executor::traits::Error::AssetNotHandled),
+					},
+				_ => Err(xcm_executor::traits::Error::AssetNotHandled),
+			}
+		}
+	}
+}