ouroboros-consensus-shelley-test: introduce CanMockPreAlonzo workaround

This is a temporary workaround; the AlonzoEra does not satisfy
CanMockPreAlonzo, so we cannot use CanMockPreAlonzo for instances that are
elsewhere required for each element of CardanoEras. Thankfully, only these uses
of CanMockPreAlonzo need the Alonzo-incompatible constraints, and these three
are also not requires of CardanoEras.

ouroboros-consensus-shelley-test/src/Test/Consensus/Shelley/Generators.hs

@@ -38,7 +38,7 @@ import           Test.Util.Serialisation.Roundtrip (Coherent (..),
 import           Test.Cardano.Ledger.AllegraEraGen ()
 import           Test.Cardano.Ledger.MaryEraGen ()
 import           Test.Cardano.Ledger.ShelleyMA.Serialisation.Generators ()
-import           Test.Consensus.Shelley.MockCrypto (CanMock)
+import           Test.Consensus.Shelley.MockCrypto (CanMock, CanMockPreAlonzo)
 import           Test.Shelley.Spec.Ledger.ConcreteCryptoTypes as SL
 import           Test.Shelley.Spec.Ledger.Generator.ShelleyEraGen ()
 import           Test.Shelley.Spec.Ledger.Serialisation.EraIndepGenerators
@@ -54,21 +54,21 @@ import           Test.Shelley.Spec.Ledger.Serialisation.Generators ()
 
 -- | The upstream 'Arbitrary' instance for Shelley blocks does not generate
 -- coherent blocks, so neither does this.
-instance CanMock era => Arbitrary (ShelleyBlock era) where
+instance CanMockPreAlonzo era => Arbitrary (ShelleyBlock era) where
   arbitrary = mkShelleyBlock <$> arbitrary
 
 -- | This uses a different upstream generator to ensure the header and block
 -- body relate as expected.
-instance CanMock era => Arbitrary (Coherent (ShelleyBlock era)) where
+instance CanMockPreAlonzo era => Arbitrary (Coherent (ShelleyBlock era)) where
   arbitrary = Coherent . mkShelleyBlock <$> genCoherentBlock
 
-instance CanMock era => Arbitrary (Header (ShelleyBlock era)) where
+instance CanMockPreAlonzo era => Arbitrary (Header (ShelleyBlock era)) where
   arbitrary = getHeader <$> arbitrary
 
 instance SL.Mock c => Arbitrary (ShelleyHash c) where
   arbitrary = ShelleyHash <$> arbitrary
 
-instance CanMock era => Arbitrary (GenTx (ShelleyBlock era)) where
+instance CanMockPreAlonzo era => Arbitrary (GenTx (ShelleyBlock era)) where
   arbitrary = mkShelleyTx <$> arbitrary
 
 instance CanMock era => Arbitrary (GenTxId (ShelleyBlock era)) where

ouroboros-consensus-shelley-test/src/Test/Consensus/Shelley/MockCrypto.hs

@@ -8,6 +8,7 @@
 module Test.Consensus.Shelley.MockCrypto (
     Block
   , CanMock
+  , CanMockPreAlonzo
   , MockCrypto
   , MockShelley
   ) where
@@ -70,5 +71,11 @@ type CanMock era =
   , Arbitrary (Core.TxOut era)
   , Arbitrary (Core.Value era)
   , Arbitrary (PredicateFailure (SL.UTXOW era))
+  )
+
+-- | A stronger 'CanMock' that is incompatible with Alonzo
+type CanMockPreAlonzo era =
+  ( CanMock era
   , Core.TxSeq era ~ SL.TxSeq era
+  , Core.Witnesses era ~ SL.WitnessSet era
   )