add a more coherent (less random) block generator

In 7447dd7 we changed genBlock to
produce blocks with more noise. This turns out to have broken some tests
in the consensus layer that relied on some coherency in the block.

See IntersectMBO/ouroboros-network#3134

To fix this, we add a new block generator genCoherentBlock, which is
almost exactly like the previous genBlock, but does not require the
PreAlonzo constraint.

shelley/chain-and-ledger/shelley-spec-ledger-test/src/Test/Shelley/Spec/Ledger/Serialisation/EraIndepGenerators.hs

@@ -17,6 +17,7 @@
 
 module Test.Shelley.Spec.Ledger.Serialisation.EraIndepGenerators
   ( mkDummyHash,
+    genCoherentBlock,
     genHash,
     genShelleyAddress,
     genByronAddress,
@@ -126,16 +127,21 @@ import qualified Shelley.Spec.Ledger.STS.Tickn as STS
 import qualified Shelley.Spec.Ledger.STS.Utxow as STS
 import Shelley.Spec.Ledger.Serialization (ToCBORGroup)
 import Shelley.Spec.Ledger.Tx (WitnessSetHKD (WitnessSet), hashScript)
+import Test.Shelley.Spec.Ledger.Generator.ScriptClass (ScriptClass)
 import Test.QuickCheck (Arbitrary, arbitrary, genericShrink, listOf, oneof, recursivelyShrink, resize, shrink, vectorOf)
 import Test.QuickCheck.Gen (chooseAny)
 import Test.Shelley.Spec.Ledger.ConcreteCryptoTypes (Mock)
 import Test.Shelley.Spec.Ledger.Generator.Constants (defaultConstants)
 import Test.Shelley.Spec.Ledger.Generator.Core
-  ( mkBlockHeader,
+  ( KeySpace (KeySpace_),
     mkOCert,
+    geKeySpace,
+    ksCoreNodes,
+    mkBlock,
+    mkBlockHeader,
   )
 import Test.Shelley.Spec.Ledger.Generator.EraGen (EraGen)
-import Test.Shelley.Spec.Ledger.Generator.Presets (coreNodeKeys)
+import Test.Shelley.Spec.Ledger.Generator.Presets (coreNodeKeys, genEnv)
 import Test.Shelley.Spec.Ledger.Serialisation.Generators.Bootstrap
   ( genBootstrapAddress,
     genSignature,
@@ -791,6 +797,50 @@ genBlock ::
   Gen (Block era)
 genBlock = Block <$> arbitrary <*> (toTxSeq @era <$> arbitrary)
 
+-- | For some purposes, a totally random block generator may not be suitable.
+-- There are tests in the ouroboros-network repository, for instance, that
+-- perform some integrity checks on the generated blocks.
+--
+-- For other purposes, such as the serialization tests in this repository,
+-- 'genBlock' is more appropriate.
+--
+-- This generator uses 'mkBlock' provide more coherent blocks.
+genCoherentBlock ::
+  forall era.
+  ( Era era,
+    ToCBORGroup (TxSeq era),
+    Mock (Crypto era),
+    ScriptClass era,
+    UsesTxBody era,
+    Arbitrary (TxInBlock era)
+  ) =>
+  Gen (Block era)
+genCoherentBlock = do
+  let KeySpace_ {ksCoreNodes} = geKeySpace (genEnv p)
+  prevHash <- arbitrary :: Gen (HashHeader (Crypto era))
+  allPoolKeys <- elements (map snd ksCoreNodes)
+  txs <- arbitrary
+  curSlotNo <- SlotNo <$> choose (0, 10)
+  curBlockNo <- BlockNo <$> choose (0, 100)
+  epochNonce <- arbitrary :: Gen Nonce
+  let kesPeriod = 1
+      keyRegKesPeriod = 1
+      ocert = mkOCert allPoolKeys 1 (KESPeriod kesPeriod)
+  return $
+    mkBlock
+      prevHash
+      allPoolKeys
+      txs
+      curSlotNo
+      curBlockNo
+      epochNonce
+      kesPeriod
+      keyRegKesPeriod
+      ocert
+  where
+    p :: Proxy era
+    p = Proxy
+
 instance
   ( Era era,
     Arbitrary (Core.TxBody era),