Assert well-funded test result is fully balanced

Author: Jimbo4350

cardano-api/test/cardano-api-test/Test/Cardano/Api/Experimental.hs

@@ -647,7 +647,7 @@ genUnderfundedTx era = do
   return (Exp.makeUnsignedTx era txBodyContent, utxo, changeAddr)
 
 -- | A well-funded transaction (UTxO >> output + fee) always produces a
--- successful positive fee calculation.
+-- successful, fully balanced result with a positive fee.
 prop_calcMinFeeRecursive_well_funded_succeeds :: Property
 prop_calcMinFeeRecursive_well_funded_succeeds = H.property $ do
   (unsignedTx, utxo, changeAddr) <- H.forAll $ genFundedSimpleTx Exp.ConwayEra
@@ -656,6 +656,16 @@ prop_calcMinFeeRecursive_well_funded_succeeds = H.property $ do
     Right (Exp.UnsignedTx resultLedgerTx) -> do
       let resultFee = resultLedgerTx ^. L.bodyTxL . L.feeTxBodyL
       H.assert $ resultFee > L.Coin 0
+      -- The resulting transaction must be fully balanced (zero balance).
+      let balance =
+            UnexportedLedger.evalBalanceTxBody
+              exampleProtocolParams
+              (const Nothing)
+              (const Nothing)
+              (const False)
+              utxo
+              (resultLedgerTx ^. L.bodyTxL)
+      balance H.=== mempty
 
 -- | 'calcMinFeeRecursive' is idempotent: applying it to its own result
 -- yields the same 'UnsignedTx'.  This confirms the fee has reached a