encoding: make Block convertible to span

Change-Id: Idb501467d1c56b95e7fdb76acda63b919fe98f85
diff --git a/tests/unit/signature-info.t.cpp b/tests/unit/signature-info.t.cpp
index 11fdff1..dff4241 100644
--- a/tests/unit/signature-info.t.cpp
+++ b/tests/unit/signature-info.t.cpp
@@ -434,8 +434,7 @@
   // encode
   auto encoded = info.wireEncode();
   BOOST_CHECK_EQUAL(info.hasWire(), true);
-  BOOST_CHECK_EQUAL_COLLECTIONS(sigInfo, sigInfo + sizeof(sigInfo),
-                                encoded.wire(), encoded.wire() + encoded.size());
+  BOOST_TEST(encoded == sigInfo, boost::test_tools::per_element());
 
   info.setValidityPeriod(vp1);
   BOOST_CHECK_EQUAL(info.hasWire(), true);