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Co-authored-by: Zied Guesmi <[email protected]>

CHANGELOG.md

@@ -1,7 +1,7 @@
 # Changelog
 
 ## vNEXT
-- Update requester/voucher debits to refund on claims amounts divisible by volume. (#28)
+- Make sponsored & non-sponsored amounts always divisible by deal volume to refund tasks fairly. (#28)
 - Add slither suggestions. (#26)
 - Drain expired vouchers and withdraw funds. (#25)
 - Add slither github action. (#24)

contracts/VoucherHub.sol

@@ -241,7 +241,7 @@ contract VoucherHub is
         }
         sponsoredAmount = Math.min(balanceOf(msg.sender), sponsoredAmount * volume);
         // Decrease sponsored amount to make sponsored & non-sponsored amounts
-        // divisible by volume in order to refund plain amounts to voucher and
+        // are divisible by volume in order to refund plain amounts to voucher and
         // requester (i.e. make sure there are no hidden remainders) in the event
         // that tasks are claimed later.
         sponsoredAmount -= sponsoredAmount % volume;

contracts/beacon/Voucher.sol

@@ -379,6 +379,7 @@ contract Voucher is Initializable, IVoucher {
         $._refundedTasks[taskId] = true;
         if (taskPrice != 0) {
             uint256 dealSponsoredAmount = $._sponsoredAmounts[dealId];
+            // The division leaves no remainder. See VoucherHub#debitVoucher().
             uint256 taskSponsoredAmount = dealSponsoredAmount / dealVolume;
             if (taskSponsoredAmount != 0) {
                 // If the voucher did fully/partially sponsor the deal then mint voucher

test/beacon/Voucher.test.ts

@@ -826,11 +826,11 @@ describe('Voucher', function () {
                     order.volume = volume;
                 }
                 const dealPrice = taskPrice * volume;
-                let dealSponsoredAmount = dealPrice > voucherValue ? voucherValue : dealPrice;
-                // Make sure dealSponsoredAmount will need to be reduced to be divisible by volume
-                expect(dealSponsoredAmount % volume).greaterThan(0);
+                let dealSponsorableAmount = voucherValue; // dealPrice > voucherValue
+                // Make sure dealSponsorableAmount is not divisible by volume
+                expect(dealSponsorableAmount % volume).greaterThan(0);
                 // Remove remainder to get expected dealSponsoredAmount
-                dealSponsoredAmount -= dealSponsoredAmount % volume;
+                let dealSponsoredAmount -= dealSponsorableAmount % volume;
                 const dealNonSponsoredAmount = dealPrice - dealSponsoredAmount;
                 expect(dealSponsoredAmount % volume).equal(0); // Both amounts should be
                 expect(dealNonSponsoredAmount % volume).equal(0); // divisible by volume