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.cpp b/firmware_handler.cpp
index 23b0925..1980760 100644
--- a/firmware_handler.cpp
+++ b/firmware_handler.cpp
@@ -9,7 +9,7 @@
 namespace blobs
 {
 
-static std::string hashBlobID = "/flash/hash";
+const std::string FirmwareBlobHandler::hashBlobID = "/flash/hash";
 
 std::unique_ptr<GenericBlobInterface>
     FirmwareBlobHandler::CreateFirmwareBlobHandler(