add test

export_test.go

@@ -1,3 +1,5 @@
 package openssl
 
 var ErrOpen = errOpen
+
+var TestNotMarshalable = &testNotMarshalable

hash.go

@@ -112,10 +112,14 @@ func SHA3_512(p []byte) (sum [64]byte) {
 }
 
 var isMarshallableCache sync.Map
+var testNotMarshalable bool // Used in tests.
 
 // isHashMarshallable returns true if the memory layout of cb
 // is known by this library and can therefore be marshalled.
 func isHashMarshallable(ch crypto.Hash) bool {
+	if testNotMarshalable {
+		return false
+	}
 	if vMajor == 1 {
 		return true
 	}

hash_test.go

@@ -39,6 +39,27 @@ func cryptoToHash(h crypto.Hash) func() hash.Hash {
 	return nil
 }
 
+func TestHashNotMarshalable(t *testing.T) {
+	h := openssl.NewSHA256()
+	state, err := h.(encoding.BinaryMarshaler).MarshalBinary()
+	if err != nil {
+		t.Fatal(err)
+	}
+	*openssl.TestNotMarshalable = true
+	defer func() {
+		*openssl.TestNotMarshalable = false
+	}()
+
+	_, err = h.(encoding.BinaryMarshaler).MarshalBinary()
+	if err == nil {
+		t.Error("expected error")
+	}
+	err = h.(encoding.BinaryUnmarshaler).UnmarshalBinary(state)
+	if err == nil {
+		t.Error("expected error")
+	}
+}
+
 func TestHash(t *testing.T) {
 	msg := []byte("testing")
 	var tests = []struct {