neotest: allow to extract account from single signer

Signed-off-by: Evgeniy Stratonikov <evgeniy@nspcc.ru>

pkg/neotest/signer.go

@@ -27,6 +27,14 @@ type Signer interface {
 	SignTx(netmode.Magic, *transaction.Transaction) error
 }
 
+// SingleSigner is a generic interface for simple one-signature signer.
+type SingleSigner interface {
+	Signer
+	// Account returns underlying account which can be used to
+	// get public key and/or sign arbitrary things.
+	Account() *wallet.Account
+}
+
 // signer represents simple-signature signer.
 type signer wallet.Account
 
@@ -35,7 +43,7 @@ type multiSigner []*wallet.Account
 
 // NewSingleSigner returns multi-signature signer for the provided account.
 // It must contain exactly as many accounts as needed to sign the script.
-func NewSingleSigner(acc *wallet.Account) Signer {
+func NewSingleSigner(acc *wallet.Account) SingleSigner {
 	if !vm.IsSignatureContract(acc.Contract.Script) {
 		panic("account must have simple-signature verification script")
 	}
@@ -63,6 +71,11 @@ func (s *signer) SignTx(magic netmode.Magic, tx *transaction.Transaction) error
 	return (*wallet.Account)(s).SignTx(magic, tx)
 }
 
+// Account implements SingleSigner interface.
+func (s *signer) Account() *wallet.Account {
+	return (*wallet.Account)(s)
+}
+
 // NewMultiSigner returns multi-signature signer for the provided account.
 // It must contain at least as many accounts as needed to sign the script.
 func NewMultiSigner(accs ...*wallet.Account) Signer {

pkg/neotest/signer_test.go

@@ -0,0 +1,16 @@
+package neotest
+
+import (
+	"testing"
+
+	"github.com/nspcc-dev/neo-go/pkg/wallet"
+	"github.com/stretchr/testify/require"
+)
+
+func TestSingleSigner(t *testing.T) {
+	a, err := wallet.NewAccount()
+	require.NoError(t, err)
+
+	s := NewSingleSigner(a)
+	require.Equal(t, s.ScriptHash(), s.Account().Contract.ScriptHash())
+}