improve errors; merge tests

Author: shyam-patel-kira

beacon-chain/core/blocks/proposer_slashing.go

@@ -16,6 +16,9 @@ import (
 	"google.golang.org/protobuf/proto"
 )
 
+// ErrCouldNotVerifyBlockHeader is returned when a block header's signature cannot be verified.
+var ErrCouldNotVerifyBlockHeader = errors.New("could not verify beacon block header")
+
 type slashValidatorFunc func(
 	ctx context.Context,
 	st state.BeaconState,
@@ -114,7 +117,7 @@ func VerifyProposerSlashing(
 	for _, header := range headers {
 		if err := signing.ComputeDomainVerifySigningRoot(beaconState, pIdx, slots.ToEpoch(hSlot),
 			header.Header, params.BeaconConfig().DomainBeaconProposer, header.Signature); err != nil {
-			return errors.Wrap(err, "could not verify beacon block header")
+			return errors.Wrap(ErrCouldNotVerifyBlockHeader, err.Error())
 		}
 	}
 	return nil

beacon-chain/sync/validate_beacon_blocks.go

@@ -3,7 +3,6 @@ package sync
 import (
 	"context"
 	"fmt"
-	"strings"
 	"time"
 
 	pubsub "github.com/libp2p/go-libp2p-pubsub"
@@ -533,7 +532,7 @@ func (s *Service) detectAndBroadcastEquivocation(ctx context.Context, blk interf
 
 	// Verify the slashing against current state
 	if err := blocks.VerifyProposerSlashing(headState, slashing); err != nil {
-		if strings.Contains(err.Error(), "could not verify beacon block header") {
+		if errors.Is(err, blocks.ErrCouldNotVerifyBlockHeader) {
 			return errors.Wrap(ErrSlashingSignatureFailure, err.Error())
 		}
 		return errors.Wrap(err, "could not verify proposer slashing")