tools: blob: add exceptions

Add exceptions on failures where it's a clean failure path.

Change-Id: Iaa8b6c7a0914367866092a7e31899453183fd7b2
Signed-off-by: Patrick Venture <venture@google.com>
diff --git a/test/tools_updater_unittest.cpp b/test/tools_updater_unittest.cpp
index d36304b..bc7417c 100644
--- a/test/tools_updater_unittest.cpp
+++ b/test/tools_updater_unittest.cpp
@@ -17,8 +17,9 @@
     BlobInterfaceMock blobMock;
     std::string firmwareImage = "image.bin";
     std::string signatureFile = "image.sig";
+    std::string expectedBlob = "/flash/image";
 
-    std::vector<std::string> blobList = {"/flash/image"};
+    std::vector<std::string> blobList = {expectedBlob};
     StatResponse statObj;
     statObj.blob_state = blobs::FirmwareBlobHandler::UpdateFlags::ipmi |
                          blobs::FirmwareBlobHandler::UpdateFlags::lpc;
@@ -29,12 +30,11 @@
 
     EXPECT_CALL(blobMock, getBlobList()).WillOnce(Return(blobList));
 
-    EXPECT_CALL(blobMock, getStat(StrEq(blobList[0].c_str())))
-        .WillOnce(Return(statObj));
+    EXPECT_CALL(blobMock, getStat(Eq(expectedBlob))).WillOnce(Return(statObj));
 
     EXPECT_CALL(handlerMock, supportedType()).WillOnce(Return(supported));
 
-    EXPECT_CALL(blobMock, openBlob(StrEq(blobList[0].c_str()), Eq(supported)))
+    EXPECT_CALL(blobMock, openBlob(StrEq(expectedBlob.c_str()), Eq(supported)))
         .WillOnce(Return(session));
 
     EXPECT_CALL(handlerMock,