Adapt the expected error to the actual message tested (#359)

* Adapt the expected error to the actuall message

* Fix an off-by-one mistake (#360)

In PR #354, I introduced a mechanism that counts how many times a given
datum is present in the MockChain, and only deletes the entry in the
'mcstDatums' once that count reaches zero. I realized just now that I
wrote the logic in such a way as to delete the entry *after* the count
has reached zero and would be decremented to -1. This means that entries
are never deleted, which defeats the memory saving purpose that of the
whole operation... This commit rectifies this.

src/Cooked/MockChain/Direct.hs

@@ -397,4 +397,4 @@ runTransactionValidation theParams cardanoTx rawModTx consumedData producedData
       return (Ledger.CardanoEmulatorEraTx cardanoTx)
   where
     addMcstDatums stored new = Map.unionWith (\(d, n1) (_, n2) -> (d, n1 + n2)) stored (Map.map (,1) new)
-    removeMcstDatums = Map.differenceWith $ \(d, n) _ -> if n == 0 then Nothing else Just (d, n - 1)
+    removeMcstDatums = Map.differenceWith $ \(d, n) _ -> if n == 1 then Nothing else Just (d, n - 1)

tests/Cooked/ReferenceScriptsSpec.hs

@@ -276,7 +276,7 @@ tests =
                       txSkelSigners = [wallet 1]
                     },
           testCase "fail from transaction generation for mismatching reference scripts" $
-            let expectedError = GenerateTxErrorGeneral "txSkelInToTxIn: The hash of the reference script and the hash of the owner of the input mismatch. Are you using the correct TxOutRef on your TxSkelRedeemerForReferencedScript?"
+            let expectedError = GenerateTxErrorGeneral "txSkelInToTxIn: Wrong reference script hash. Are you using the correct TxOutRef on your TxSkelRedeemerForReferencedScript?"
              in testFailsFrom
                   def
                   ( \case