Add test for max lenght varint

cid_test.go

@@ -119,6 +119,15 @@ func TestPrefixRoundtrip(t *testing.T) {
 	}
 }
 
+func Test16BytesVarint(t *testing.T) {
+	data := []byte("this is some test content")
+	hash, _ := mh.Sum(data, mh.SHA2_256, -1)
+	c := NewCidV1(CBOR, hash)
+
+	c.codec = 1 << 54
+	_ = c.Bytes()
+}
+
 func TestFuzzCid(t *testing.T) {
 	buf := make([]byte, 128)
 	for i := 0; i < 200; i++ {