tests: use decorators to disable test data generators by default

Change-Id: I7f58bc4f939a6040f0dab647f07b9c29a4a16b4e
diff --git a/tests/unit/decryptor.t.cpp b/tests/unit/decryptor.t.cpp
index 940a990..e7c2a0f 100644
--- a/tests/unit/decryptor.t.cpp
+++ b/tests/unit/decryptor.t.cpp
@@ -116,10 +116,10 @@
                     [&] (ConstBufferPtr buffer) {
                       ++nSuccesses;
                       BOOST_CHECK_EQUAL(buffer->size(), 15);
-                      std::string content(reinterpret_cast<const char*>(buffer->data()), buffer->size());
+                      std::string content(buffer->get<char>(), buffer->size());
                       BOOST_CHECK_EQUAL(content, "Data to encrypt");
                     },
-                    [&] (const ErrorCode& code, const std::string& msg) {
+                    [&] (const ErrorCode&, const std::string& msg) {
                       BOOST_TEST_MESSAGE(msg);
                       ++nFailures;
                     });