Add class interface BinaryStore for storage abstraction

Represent each storage location as a separate class instance. Add an
interface BinaryStore for this purpose, and add basic unit tests
using a mock.

Signed-off-by: Kun Yi <kunyi@google.com>
Change-Id: I67a140280985db567a4f31d0fe5439105b0a47f9
diff --git a/test/handler_unittest.hpp b/test/handler_unittest.hpp
index fd93de4..f6390fc 100644
--- a/test/handler_unittest.hpp
+++ b/test/handler_unittest.hpp
@@ -1,5 +1,6 @@
 #pragma once
 
+#include "binarystore_mock.hpp"
 #include "handler.hpp"
 
 #include <gtest/gtest.h>
@@ -11,12 +12,7 @@
 {
   protected:
     BinaryStoreBlobHandlerTest() = default;
-
-    BinaryStoreBlobHandler bstore;
-};
-
-class BinaryStoreBlobHandlerBasicTest : public BinaryStoreBlobHandlerTest
-{
+    BinaryStoreBlobHandler handler;
 };
 
 } // namespace blobs