security: sign and verify new signed Interest format

refs #4804

Change-Id: Ib819edb977fa06c670b04185a0d730203c7d7fdb
diff --git a/tests/unit/security/digest-sha256.t.cpp b/tests/unit/security/digest-sha256.t.cpp
index 8b5e11d..674aaf5 100644
--- a/tests/unit/security/digest-sha256.t.cpp
+++ b/tests/unit/security/digest-sha256.t.cpp
@@ -61,6 +61,7 @@
 {
   Name name("/SecurityTestDigestSha256/InterestSignature/Interest1");
   Interest testInterest(name);
+  testInterest.setCanBePrefix(false);
 
   m_keyChain.sign(testInterest, security::SigningInfo(security::SigningInfo::SIGNER_TYPE_SHA256));
   verifyDigest(testInterest, DigestAlgorithm::SHA256);