Fix missing instances

Author: tbagrel1

ouroboros-consensus/test/storage-test/Test/Ouroboros/Storage/PerasCertDB/StateMachine.hs

@@ -11,6 +11,7 @@ import Ouroboros.Consensus.Block.SupportsPeras
 import Test.Ouroboros.Storage.PerasCertDB.Model
 import Test.QuickCheck.StateModel
 import Ouroboros.Consensus.Storage.PerasCertDB.API (PerasWeightSnapshot)
+import Ouroboros.Consensus.Storage.PerasCertDB (PerasCertDbError)
 
 tests :: TestTree
 tests = undefined
@@ -22,8 +23,14 @@ instance StateModel Model where
   data Action Model a where
     OpenDB :: Action Model ()
     CloseDB :: Action Model ()
-    AddCert :: PerasCert Block -> Action Model ()
-    GetWeightSnapshot :: Action Model (PerasWeightSnapshot Block)
+    AddCert :: PerasCert Block -> Action Model (Either PerasCertDbError ())
+    GetWeightSnapshot :: Action Model (Either PerasCertDbError (PerasWeightSnapshot Block))
 
   arbitraryAction _ _ = error "arbitraryAction not implemented"
   initialState = error "initialState not implemented"
+
+deriving instance Show (Action Model a)
+
+instance HasVariables (Action Model a) where
+  getAllVariables _ = mempty
+