4 files changed, 29 insertions, 19 deletions
diff --git a/internal/mocks/signer/signer.go b/internal/mocks/signer/signer.go
new file mode 100644
index 0000000..a4ec30d
--- /dev/null
+++ b/internal/mocks/signer/signer.go
@@ -0,0 +1,22 @@
+package signer
+
+import (
+	"crypto"
+	"crypto/ed25519"
+	"io"
+)
+
+// Signer implements crypto.Signer with fixed outputs.  Use for tests only.
+type Signer struct {
+	PublicKey []byte
+	Signature []byte
+	Error     error
+}
+
+func (s *Signer) Public() crypto.PublicKey {
+	return ed25519.PublicKey(s.PublicKey[:])
+}
+
+func (s *Signer) Sign(rand io.Reader, digest []byte, opts crypto.SignerOpts) ([]byte, error) {
+	return s.Signature[:], s.Error
+}
diff --git a/pkg/types/crypto_test.go b/pkg/types/crypto_test.go
index d95d5fa..181c8f0 100644
--- a/pkg/types/crypto_test.go
+++ b/pkg/types/crypto_test.go
@@ -4,24 +4,9 @@ import (
 	"crypto"
 	"crypto/ed25519"
 	"crypto/rand"
-	"io"
 	"testing"
 )
 
-type testSigner struct {
-	PublicKey PublicKey
-	Signature Signature
-	Error     error
-}
-
-func (ts *testSigner) Public() crypto.PublicKey {
-	return ed25519.PublicKey(ts.PublicKey[:])
-}
-
-func (ts *testSigner) Sign(rand io.Reader, digest []byte, opts crypto.SignerOpts) ([]byte, error) {
-	return ts.Signature[:], ts.Error
-}
-
 func newKeyPair(t *testing.T) (crypto.Signer, PublicKey) {
 	vk, sk, err := ed25519.GenerateKey(rand.Reader)
 	if err != nil {
diff --git a/pkg/types/leaf_test.go b/pkg/types/leaf_test.go
index 645f49e..9eae13c 100644
--- a/pkg/types/leaf_test.go
+++ b/pkg/types/leaf_test.go
@@ -8,6 +8,8 @@ import (
 	"reflect"
 	"strings"
 	"testing"
+
+	"git.sigsum.org/sigsum-go/internal/mocks/signer"
 )
 
 func TestStatementToBinary(t *testing.T) {
@@ -28,13 +30,13 @@ func TestStatementSign(t *testing.T) {
 		{
 			desc:    "invalid: signer error",
 			stm:     validStatement(t),
-			signer:  &testSigner{*newPubBufferInc(t), *newSigBufferInc(t), fmt.Errorf("signing error")},
+			signer:  &signer.Signer{newPubBufferInc(t)[:], newSigBufferInc(t)[:], fmt.Errorf("signing error")},
 			wantErr: true,
 		},
 		{
 			desc:    "valid",
 			stm:     validStatement(t),
-			signer:  &testSigner{*newPubBufferInc(t), *newSigBufferInc(t), nil},
+			signer:  &signer.Signer{newPubBufferInc(t)[:], newSigBufferInc(t)[:], nil},
 			wantSig: newSigBufferInc(t),
 		},
 	} {
diff --git a/pkg/types/tree_head_test.go b/pkg/types/tree_head_test.go
index a1ffa6f..aa57a1c 100644
--- a/pkg/types/tree_head_test.go
+++ b/pkg/types/tree_head_test.go
@@ -8,6 +8,7 @@ import (
 	"reflect"
 	"testing"
 
+	"git.sigsum.org/sigsum-go/internal/mocks/signer"
 	"git.sigsum.org/sigsum-go/pkg/hex"
 )
 
@@ -30,13 +31,13 @@ func TestTreeHeadSign(t *testing.T) {
 		{
 			desc:    "invalid: signer error",
 			th:      validTreeHead(t),
-			signer:  &testSigner{*newPubBufferInc(t), *newSigBufferInc(t), fmt.Errorf("signing error")},
+			signer:  &signer.Signer{newPubBufferInc(t)[:], newSigBufferInc(t)[:], fmt.Errorf("signing error")},
 			wantErr: true,
 		},
 		{
 			desc:    "valid",
 			th:      validTreeHead(t),
-			signer:  &testSigner{*newPubBufferInc(t), *newSigBufferInc(t), nil},
+			signer:  &signer.Signer{newPubBufferInc(t)[:], newSigBufferInc(t)[:], nil},
 			wantSig: newSigBufferInc(t),
 		},
 	} {