security: rename SignatureSha256 to DigestSha256

Change-Id: Idabb95222d86e2541372593698ed9754156a5df2
diff --git a/tests/unit-tests/test-interest.cpp b/tests/unit-tests/test-interest.cpp
index 5bb0a85..f02a8a8 100644
--- a/tests/unit-tests/test-interest.cpp
+++ b/tests/unit-tests/test-interest.cpp
@@ -22,7 +22,7 @@
 #include "interest.hpp"
 #include "data.hpp"
 #include "security/signature-sha256-with-rsa.hpp"
-#include "security/signature-sha256.hpp"
+#include "security/digest-sha256.hpp"
 #include "encoding/buffer-stream.hpp"
 
 #include "boost-test.hpp"
@@ -492,7 +492,7 @@
   interest.setPublisherPublicKeyLocator(KeyLocator("ndn:/B"));
 
   Data data4 = data;
-  SignatureSha256 signature4; // violates PublisherPublicKeyLocator
+  DigestSha256 signature4; // violates PublisherPublicKeyLocator
   data4.setSignature(signature4);
   data4.wireEncode();
   BOOST_CHECK_EQUAL(interest.matchesData(data4), false);