test: Add first unit-test to verify factory

Verify the factory does what we expect.

Change-Id: Ied4fbe45b1b46c0cc5726c9d5e437a9cb92e6182
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/firmware_handler.hpp b/firmware_handler.hpp
index 3eede31..f5239b4 100644
--- a/firmware_handler.hpp
+++ b/firmware_handler.hpp
@@ -67,6 +67,8 @@
     bool stat(uint16_t session, struct BlobMeta* meta) override;
     bool expire(uint16_t session) override;
 
+    static const std::string hashBlobID;
+
   private:
     std::vector<std::string> blobIDs;
     std::uint32_t transports;