cryptutil: fix potential race with signer

internal/cryptutil/mock_cipher_test.go

@@ -0,0 +1,44 @@
+package cryptutil // import "github.com/pomerium/pomerium/internal/cryptutil"
+
+import (
+	"errors"
+	"testing"
+)
+
+func TestMockCipher_Unmarshal(t *testing.T) {
+	e := errors.New("err")
+	mc := MockCipher{
+		EncryptResponse: []byte("EncryptResponse"),
+		EncryptError:    e,
+		DecryptResponse: []byte("DecryptResponse"),
+		DecryptError:    e,
+		MarshalResponse: "MarshalResponse",
+		MarshalError:    e,
+		UnmarshalError:  e,
+	}
+	b, err := mc.Encrypt([]byte("test"))
+	if string(b) != "EncryptResponse" {
+		t.Error("unexpected encrypt response")
+	}
+	if err != e {
+		t.Error("unexpected encrypt error")
+	}
+	b, err = mc.Decrypt([]byte("test"))
+	if string(b) != "DecryptResponse" {
+		t.Error("unexpected Decrypt response")
+	}
+	if err != e {
+		t.Error("unexpected Decrypt error")
+	}
+	s, err := mc.Marshal("test")
+	if err != e {
+		t.Error("unexpected Marshal error")
+	}
+	if s != "MarshalResponse" {
+		t.Error("unexpected MarshalResponse error")
+	}
+	err = mc.Unmarshal("s", "s")
+	if err != e {
+		t.Error("unexpected Unmarshal error")
+	}
+}